JP2013145180A - Radiation detector, radiation detection assembly and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector that depletes a whole substrate, reduces a diffusion layer capacity, and enables fast detection with high sensitivity, and an operation method thereof.SOLUTION: A radiation detector comprises an I layer 11 composed of a silicon substrate or the like, a P type diffusion layer 12 provided on a first face of a substrate, an island-shaped N type diffusion layer 13 provided in the center of a second face of the substrate, and a gate electrode 14 formed over the whole area of the second face of the substrate so as to surround the N type diffusion layer 13 with a gate insulator 15 being interposed therebetween.

Description

  The present invention relates to a radiation detector, a radiation detection apparatus, and an operation method thereof using a high-resistance semiconductor substrate such as silicon.

  Conventionally, as a radiation detector, SDD (Semiconductor Drift Detector) has been proposed, which is capable of detecting high-energy radiation such as X-rays with high sensitivity by depleting the high-resistance semiconductor substrate itself and forming a thick photoelectric conversion layer. Has been. In this SDD, the anode is an annular multi-electrode, and when detecting radiation, different electric potentials are applied to the multi-electrode to form a potential gradient to increase the charge collection efficiency, and a diffusion layer is provided at the center of the substrate surface. By forming locally, the capacity of the diffusion layer is reduced, and as a result, it is suitable for high-speed operation and the energy resolution is improved.

  FIG. 5 is a partially omitted cross-sectional view showing an example of the structure of the SDD having such a configuration disclosed in Japanese Patent Laid-Open No. 2008-153256 (Patent Document 1). In the SDD shown in FIG. 5, a P-type diffusion layer (cathode) 112 is provided on the first surface 111 (back surface) of the I layer 110 made of a silicon substrate, and on the second surface (front surface) 113 of the I layer 110. An N-type diffusion layer (anode) 114 is provided, and a number of P-ring diffusion layers 115a, 115b, and 115c are formed around the N-type diffusion layer 114.

The resistivity of the I layer 110 is usually 1 kΩcm or more and the thickness thereof is 100 μm or more. On the other hand, the P-type diffusion layer 112 or the N-type diffusion layer 114 has, for example, a surface concentration value of 1E20 cm. ^-3, the diffusion layer depth is to be about 1 [mu] m.

  In the conventional SDD having such a configuration, a voltage is applied to the P-type diffusion layer 112 of the first surface 111, and the P-ring type diffusion layers 115a, 115b, and 115c are respectively shown in FIG. By applying a large voltage, the potential gradient generated by the voltage can efficiently collect charges (electrons) generated in the I layer 110 by the incidence of radiation in the N-type diffusion layer 114.

JP 2008-153256 A

  By the way, in the SDD disclosed in the above-mentioned Patent Document 1, the influence of the bias of the N-type diffusion layer 114 formed at the center of the surface decreases as it comes to the periphery of the device, as can be inferred from the description of the structure and operation. The depletion caused by the reverse bias of the diode on the silicon substrate is impaired, resulting in a decrease in the photoelectric conversion capability of the diode, and a reduction in the N-type diffusion layer capacitance compared to a radiation detector comprising a conventional PIN diode. Although there is a high speed based on this, there has been a drawback that the sensitivity of the sensor is lowered.

  Further, since different bias voltages are applied to the P-ring type diffusion layers 115a, 115b, and 115c formed on the surface, current flows between the P-ring type diffusion layers, and in addition, each P-ring type diffusion layer 115a, 115b. , 115c and the P-type diffusion layer 112 formed on the first surface 111 of the silicon substrate, heat is generated due to an increase in power consumption caused by the current. There has also been a problem of increasing the current, that is, increasing the noise current with respect to the signal current.

  The present invention has been made to solve the above-described problems in radiation detectors such as conventional SSDs, and at the time of photoelectric conversion operation, the entire substrate can be depleted like a radiation detector composed of a conventional PIN diode. Therefore, during the signal readout operation, the capacitance of the diffusion layer coupled to the external signal detection circuit can be reduced, that is, CR (capacitance). It is an object of the present invention to provide a radiation detector and radiation detection apparatus capable of high-speed operation and high sensitivity, and a method for operating them, in which the time constant determined by the (resistance) product can be reduced. Furthermore, an object of the present invention is to provide a radiation detector, a radiation detection apparatus, and an operation method thereof that can prevent an unnecessary current flow and can realize low power consumption, low heat generation, and low noise as compared with a conventional SDD. And

  In order to achieve the above object, an invention according to claim 1 includes a high-resistance semiconductor substrate, a P-type diffusion layer provided on a first surface of the high-resistance semiconductor substrate, and a second of the high-resistance semiconductor substrate. An N-type diffusion layer provided in an island shape on the surface, and a gate electrode formed on the entire surface of the second surface of the high-resistance semiconductor substrate so as to surround the N-type diffusion layer with a gate insulating film interposed therebetween. Thus, the radiation detector is constituted.

  In the radiation detector configured in this way, since the inversion layer under the gate electrode, that is, the presence or absence of electric charge can be controlled by the bias applied to the gate electrode, the entire structure of the high-resistance semiconductor substrate is depleted with a simple configuration. A radiation detector that can achieve both high sensitivity and high-speed operation by reducing the diffusion layer capacitance in the island-shaped N-type diffusion layer can be realized.

  According to a second aspect of the present invention, in the radiation detector according to the first aspect, a low concentration N is formed so as to surround the N-type diffusion layer on the surface portion of the second surface of the high-resistance semiconductor substrate immediately below the gate electrode. A mold surface layer is formed.

  In the radiation detector configured as described above, the gate threshold potential can be adjusted by the low concentration N-type surface layer, and the bias potential applied to the gate electrode can be optimized.

  The invention according to claim 3 is the radiation detector according to claim 2, characterized in that the impurity concentration of the low-concentration N-type surface layer increases as it approaches the N-type diffusion layer. It is.

  In the radiation detector configured as described above, it is possible to further increase the movement speed of the signal charge generated on the high-resistance semiconductor substrate by the incidence of radiation to the N-type diffusion layer (anode), so that a higher-speed signal can be obtained. Reading is possible.

  According to a fourth aspect of the present invention, in the radiation detector according to any one of the first to third aspects, the thickness of the gate insulating film decreases as the thickness approaches the N-type diffusion layer. It is what.

  In the radiation detector configured as described above, it is possible to further increase the movement speed of the signal charge generated on the high-resistance semiconductor substrate by the incidence of radiation to the N-type diffusion layer (anode), so that a higher-speed signal can be obtained. Reading is possible.

  The invention according to claim 5 is a high-resistance semiconductor substrate, a P-type diffusion layer provided in an island shape on the first surface of the high-resistance semiconductor substrate, and the high-resistance semiconductor so as to surround the P-type diffusion layer A first gate electrode formed on the entire first surface of the substrate with a gate insulating film interposed therebetween, an N-type diffusion layer provided in an island shape on the second surface of the high-resistance semiconductor substrate, A radiation detector is constituted by a second gate electrode formed on the entire second surface of the high-resistance semiconductor substrate with a gate insulating film interposed so as to surround the N-type diffusion layer. .

  In the radiation detector configured in this way, it is possible to reduce the capacitance of the P-type and N-type diffusion layers on the first and second surfaces of the high-resistance semiconductor substrate, thereby enabling higher-speed operation. A radiation detector can be realized.

  The invention according to claim 6 constitutes a radiation detection apparatus by superimposing a plurality of radiation detectors according to any one of claims 1 to 4.

  According to a seventh aspect of the present invention, a plurality of radiation detectors according to the fifth aspect are overlapped to constitute a radiation detection apparatus.

  In the radiation detection apparatus configured as described above, a more sensitive radiation detection apparatus can be realized by outputting the outputs of the detectors in parallel.

  According to an eighth aspect of the present invention, in the radiation detector according to any one of the first to fourth and sixth aspects, an inversion layer exists under the gate electrode during the signal accumulation operation, and under the gate electrode during the signal readout operation. The operation method of the radiation detector or the radiation detection apparatus is configured so as to operate in the state where the inversion layer does not exist.

  According to a ninth aspect of the present invention, in the radiation detector according to the fifth or seventh aspect, the inversion layer exists under the first and second gate electrodes during the signal accumulation operation, and the first and second during the signal readout operation. The operation method of the radiation detector or the radiation detection apparatus is configured so as to operate in a state where no inversion layer exists under the gate electrode.

  In the operation method of the radiation detector or radiation detection apparatus configured as described above, high-speed operation by reducing the N-type diffusion layer capacitance and high-sensitivity operation by depletion of the entire high-resistance semiconductor substrate can be easily performed. it can.

  According to the present invention, compared to conventional radiation detectors, a radiation detector and a radiation detection apparatus, and their operation methods, which have a simple configuration, can be detected with higher sensitivity and can be detected at high speed, and have low power consumption. can do.

It is the top view and sectional drawing for demonstrating 1st Embodiment of the radiation detector which concerns on this invention. It is a chart for demonstrating operation | movement of the radiation detector shown in FIG. It is sectional drawing for demonstrating 2nd Embodiment based on this invention. It is sectional drawing for demonstrating the 3rd Embodiment concerning this invention. It is a partially omitted cross-sectional view for explaining a configuration example of a conventional SDD.

  Hereinafter, modes for carrying out the present invention will be described.

(First embodiment)
1A and 1B show a first embodiment of a radiation detector according to the present invention. 1A is a plan view seen from above the radiation detector according to the present embodiment, and FIG. 1B is a cross-sectional view of the radiation detector shown in FIG. 1A and 1B, reference numeral 11 denotes an I layer made of a semiconductor substrate such as silicon, which is used as a substrate. The resistivity of the I layer 11 is usually 1 kΩcm or more, preferably 10 kΩcm or more. For example, in order to fully deplete a substrate having a thickness of 500 μm by applying a potential of 100 V, a substrate concentration of 5.3E11 cm ⁻³ (that is, corresponding to about 10 kΩcm in the case of an N-type substrate) is required. . Further, by using a high-resistance substrate, the applied voltage can be reduced.

  In addition, the thickness of the semiconductor substrate (I layer) is 100 μm or more, and preferably 500 μm or more. This is because the radiation detection sensitivity increases as the depleted substrate becomes thicker.

  The type of impurities in the semiconductor substrate is not particularly limited, but when the signal carrier is an electron, the P type is desirable. When the semiconductor is silicon, P-type impurities such as boron are included in the I layer (substrate).

A P-type diffusion layer (cathode) 12 is provided on the first surface (back surface) of the I layer, as in the conventional SDD. The P-type diffusion layer 12 has a surface concentration value of 1E19 cm ⁻³ or more, preferably 1E20 cm ⁻³ or more. The diffusion layer depth is about 1 μm.

On the other hand, an island-like N-type diffusion layer (anode) 13 is provided at the center of the second surface (front surface) of the I layer 11, as in the conventional SDD. The surface concentration value of the N-type diffusion layer 13 is preferably 1E20 cm ⁻³ or more and the diffusion layer depth is about 1 μm, but together with the P-type diffusion layer 12, the source / drain diffusion layer of a normal MOSFET, Alternatively, the structure parameter of the emitter of the bipolar transistor can be used at all.

  In the conventional SDD, a large number of P-ring type diffusion layers 115a to 115c are formed around the N-type diffusion layer 114. However, in the present invention, the gate electrode 14 is formed so as to surround the N-type diffusion layer 13. Is formed. Examples of the material of the gate electrode 14 include aluminum, polycrystalline silicon, and a refractory metal. The thickness of the gate electrode 14 is about 0.1 μm to 1 μm.

A gate insulating film 15 made of SiO ₂ or SiN is formed between the gate electrode 14 and the substrate (I layer) 11. The gate insulating film 15 is formed of the gate electrode 14 and the substrate (I layer) 11. The thickness is 0.1 μm to 1 μm, depending on the magnitude of the bias applied between the gate electrode 14 and the substrate (I layer) 11. .

  The thickness of the gate insulating film 15 is based on the premise that it is not broken by the bias applied to the gate electrode 14, and if it is assumed that a potential of about 200 V is applied to the gate electrode 14, it is 300 nm (0.3 μm). A thickness of about is desirable. In general, the withstand voltage increases as the thickness of the gate insulating film 15 increases. On the other hand, as the thickness of the gate insulating film 15 increases, the efficiency of the potential applied to the gate electrode 14 decreases. It is not a good idea to make it thick.

Further, when the voltage applied to the P-type diffusion layer (cathode) 12 is −100 V, the boron concentration of the substrate (I layer) 11 is 5E11 cm ^−3, and the gate insulating film 15 made of SiO ₂ with a thickness of 300 nm is used, If the bias applied to the N-type diffusion layer (anode) 13 on the surface is the ground potential (0 V), even if the back gate effect is taken into consideration, the gate in which the electron inversion layer is formed directly under the gate insulating film 15 The potential is calculated as 0.35V. That is, when a potential that is positive by several volts with respect to the potential applied to the N-type diffusion layer (anode) 13 is applied to the gate electrode 14, an electron inversion layer is formed. This low voltage property is due to the low substrate impurity concentration.

  Although FIG. 1B shows a structure in which the gate insulating film 15 has a constant thickness, the gate insulating film 15 may be set so that its thickness decreases as it approaches the N-type diffusion layer 13. In this case, for example, when the thickness of the gate insulating film 15 in the portion adjacent to the N-type diffusion layer 13 is 300 nm, the thickness of the gate insulating film 15 at the other end is set to 600 nm, for example. Good.

Further, in FIG. 1B, 16 is a low-concentration surface impurity diffusion layer formed below the gate insulating film 15 and has a maximum surface concentration of 1E17 cm ⁻³ and a diffusion layer depth of about 1 μm. It is set in the parameter. The impurity type of the low-concentration surface impurity diffusion layer 16 is N-type, and phosphorus or arsenic atoms are diffused and formed by an ion implantation method or the like. The concentration of the low-concentration surface impurity diffusion layer 16 may be a diffusion layer structure in which the concentration increases as it approaches the N-type diffusion layer (anode) 13 in addition to the case where the entire region is constant.

The low-concentration surface impurity diffusion layer 16 has the same function as the surface impurity ion-implanted layer for adjusting the gate voltage in the case of MOSFET. Although depending on the impurity concentration of the substrate (I layer) 11 and the device operation application bias, the ion implantation dose is in the range of 1E11 cm ^{−2 to} 1E13 cm ⁻² .

  As described above, the low-concentration surface impurity diffusion layer (N-type) 16 is a layer formed for adjusting the gate threshold potential, and in particular, its concentration is increased as it approaches the N-type diffusion layer (anode) 13. As a result, a fringe electric field due to the concentration distribution is formed, and the role of rapidly inflowing electrons generated by the photoelectric conversion operation into the N-type diffusion layer region is achieved. This function can also be realized by making the gate insulating film 15 thinner as it approaches the N-type diffusion layer (anode) 13 as described above.

  Further, as shown in FIG. 1B, the gate electrode 14 and the N-type diffusion layer 13 are arranged in an overlapping manner, and their end portions are in contact with each other via the gate insulating film 15. It is in a state.

  The above is the description of the cross-sectional structure of the radiation detector according to the present embodiment shown in FIG. 1B, and the planar structure is the central portion of the surface of the radiation detector as shown in FIG. An N-type diffusion layer (anode) 13 is present on the front surface, and a gate electrode 14 is formed on the front surface so as to surround the N-type diffusion layer (anode). Has been. In addition, although the shape of the peripheral part of the gate electrode 14 or each diffusion layer 12 and 13 is shown here circular, the surface peripheral shape may be a rectangle etc., and is not limited to a circle.

  Next, the operation of the radiation detector according to the present exemplary embodiment will be described using the chart of FIG. As shown in the chart of FIG. 2, there are three operation modes: a reset operation, a photoelectric conversion operation (signal accumulation operation), and a signal readout operation. Show. On the other hand, the vertical column shows three component parts (parts) of the radiation detector, that is, a P-type diffusion layer (cathode) 12, an N-type diffusion layer (anode) 13, and a gate electrode 14. The table shows the bias applied to each component part during each operation.

  First, the P-type diffusion layer (cathode) 12 formed on the back surface is always grounded and a ground potential is applied. In this state, at the time of resetting, in order to completely discharge electrons, which are signal charges, to the N-type diffusion layer 13 serving as an anode and the substrate (I layer) 11, a positive potential of + V is applied to the N-type diffusion layer 13, and the gate electrode Similarly, a positive potential + Vg1 is applied to 14 to form a surface channel when electrons are present.

  After the reset operation, the N-type diffusion layer (anode) 13 is set in a floating state in order to accumulate electrons as signals, that is, in a photoelectric conversion state. With this operation, the N-type diffusion layer 13 is maintained at a potential of + V at the start of signal accumulation. However, as the electrons accumulate, the potential decreases in the negative direction. Further, during the photoelectric conversion operation, a potential of + Vg1 is applied to the gate electrode 14 as in the reset operation to form a surface channel (inversion layer) of signal electrons under the gate electrode, and the bias state of the substrate 11 Is set to the same state as the PIN diode. That is, the entire substrate is depleted.

  When the photoelectric conversion operation state for a certain period has passed, the operation proceeds to a signal reading operation, and the signal electrons accumulated in the N-type diffusion layer 13 are read. Therefore, a potential of + V is applied to the N-type diffusion layer 13, and accumulated signal electrons flow out from the N-type diffusion layer 13. At this time, for example, a negative potential, −Vg 2, is applied to the gate electrode 14 to bring the substrate surface into a state where there is no electron inversion layer, that is, a depletion layer state or a hole accumulation state. By setting in this state, at the time of signal readout, the diffusion capacity of the N-type diffusion layer 13 becomes the capacity of only the island-shaped N-type diffusion layer region formed on the substrate surface, similar to the SDD, and the capacitance value is reduced. Can be realized.

  Although the structure and operation of the radiation detector according to the first embodiment have been described above, the substrate of the radiation detector can be formed of a material other than silicon, for example, a compound semiconductor such as GaAs or CdTe. In particular, the heavier the atomic weight of the constituent elements, the higher the sensitivity because radiation stopping power increases.

  Also in the radiation detector according to this embodiment, radiation can correspond to incident from both directions of front side incidence and rear side incidence. Further, a signal detection device such as a circuit for detecting signal charges in the N-type diffusion layer 13 or a junction FET can be integrally formed on-chip, and this state is also a modification of the present embodiment. Included as In addition, the radiation detector according to this embodiment includes a radiation detector in a mode in which the impurity type of each diffusion layer and the bias applied to each part are reversed.

  As other modifications of the first embodiment, there are the following forms. That is, in the radiation detector according to the first embodiment shown in FIG. 1, the N-type diffusion layer (anode) is formed at one place in the center of the surface, but is not limited thereto. For example, a plurality of N-type diffusion layers can be scattered and arranged under the gate electrode on the surface of the substrate. In this case, the plurality of N-type diffusion layers are commonly connected by wiring. Also in this case, the gate electrode is arranged so as to surround each of the plurality of scattered N-type diffusion layers. By adopting such a configuration, it is possible to discharge signal electrons to the N-type diffusion layer (anode) more efficiently even for a wider gate region. Even when a single N-type diffusion layer is formed, it can be formed in the peripheral region of the gate electrode by removing the center of the device.

  As described above, according to the radiation detector according to the first embodiment and the modification thereof, the entire substrate can be depleted at the time of photoelectric conversion, and high sensitivity can be realized. Since the diffusion layer capacitance is reduced to an island-type N-type diffusion layer capacitance, high-speed device operation is also realized. In addition, the gate electrode is electrically insulated by a gate insulating film, and since two types of diffusion layers are always applied with a reverse bias, there is no direct current path as in the conventional SDD, resulting in low power consumption. Electricity is also realized.

(Second Embodiment)
Next, the configuration and operation of the radiation detector according to the second embodiment will be described with reference to FIG. FIG. 3 is a diagram showing a device cross-sectional structure of the radiation detector according to the second exemplary embodiment. The radiation detector according to this embodiment differs from the radiation detector according to the first embodiment shown in FIGS. 1A and 1B in the first embodiment on the back surface of the substrate. Whereas the P-type diffusion layer (cathode) is formed on almost the entire surface, in the present embodiment, like the surface structure, the P-type diffusion layer 12a is locally (island-like) at the center of the back surface of the substrate. In other words, the second gate electrode 14b is surrounded by the second gate electrode 14b. Then, similarly to the first gate insulating film 15a provided between the first gate electrode 14a provided on the substrate surface and the substrate (I layer) 11, the second gate electrode 14b and the substrate (I layer) 11 are provided. Between the two, a second gate insulating film 15b is formed. That is, although it is a reverse type, the point which employ | adopts the back surface structure similar to the surface structure is the characteristic of the radiation detector which concerns on 2nd Embodiment.

  Regarding the operation of the radiation detector according to the second embodiment configured as described above, the polarity of the bias is reversed, but the operation of the P-type diffusion layer 12a is the N-type diffusion layer of the chart shown in FIG. The operation of the second gate electrode is the same as that of the first gate electrode.

  In the radiation detector according to this embodiment as well, as in the radiation detector according to the first embodiment, in order to adjust the threshold potential and increase the discharge rate of holes to the P-type diffusion layer, the first detector Similar to the low-concentration surface impurity diffusion layer 16 immediately below the gate insulating film 15a, a low-concentration surface impurity diffusion layer (low-concentration boron ion implantation layer) is formed at the substrate back surface interface immediately below the second gate insulating film 15b. You can also

  As described above, in the radiation detector according to the present embodiment, the P-type diffusion layer (cathode) is also reduced in size as compared with the radiation detector according to the first embodiment. That is, since the opposite type diffusion layer facing the N-type diffusion layer (anode) is reduced, the mutual diffusion layer capacity can be further reduced, so that higher device speed can be realized.

(Third embodiment)
Next, the configuration of the radiation detector according to the third exemplary embodiment will be described with reference to FIG. As shown in FIG. 4, in the radiation detector according to the present embodiment, a plurality of radiation detectors according to the first embodiment or the second embodiment are provided, and in the aspect shown in FIG. It is configured by overlapping each other. This form constitutes a radiation detection apparatus. FIG. 4 shows a mode in which the two radiation detectors are mounted and separated (the mounting configuration is not shown), but there may be a mode in which the two radiation detectors are closely bonded via an insulating film as appropriate. .

  Since the individual configuration and operation of the radiation detector in this embodiment are the same as those of the radiation detector according to the first embodiment or the second embodiment, description thereof is omitted here. As the effect, in addition to the effect in the radiation detector according to the first embodiment or the second embodiment, the thickness of the photoelectric conversion layer as viewed from the incident direction of the radiation is Therefore, the detection sensitivity can be further increased in proportion to the number of overlapping stages. The detection output is obtained by connecting the outputs of the radiation detectors in parallel.

  As described above, according to the radiation detector (radiation detection apparatus) according to the present embodiment, the radiation detector (radiation) has higher sensitivity, higher speed, and lower power consumption than the conventional radiation detector. It has an excellent effect that a detection device) can be realized.

11 I layer (substrate)
12 P-type diffusion layer 12a P-type diffusion layer 13 N-type diffusion layer 14 Gate electrode 14a First gate electrode 14b Second gate electrode 15 Gate insulating film 15a First gate insulating film 15b Second gate insulating film 16 Low Concentration surface impurity diffusion layer

Claims (9)

  A high-resistance semiconductor substrate, a P-type diffusion layer provided on the first surface of the high-resistance semiconductor substrate, an N-type diffusion layer provided in an island shape on the second surface of the high-resistance semiconductor substrate, A radiation detector comprising: a gate electrode formed on an entire surface of the second surface of the high-resistance semiconductor substrate with a gate insulating film interposed so as to surround an N-type diffusion layer.     2. The low concentration N-type surface layer is formed on the surface portion of the second surface of the high-resistance semiconductor substrate immediately below the gate electrode so as to surround the N-type diffusion layer. Radiation detector.   The radiation detector according to claim 2, wherein the impurity concentration of the low-concentration N-type surface layer increases as the N-type diffusion layer approaches the N-type diffusion layer.   The radiation detector according to claim 1, wherein a thickness of the gate insulating film decreases as the thickness of the gate insulating film approaches the N-type diffusion layer.   A high-resistance semiconductor substrate; a P-type diffusion layer formed in an island shape on the first surface of the high-resistance semiconductor substrate; and an entire surface of the first surface of the high-resistance semiconductor substrate so as to surround the P-type diffusion layer A first gate electrode formed with a gate insulating film interposed therebetween, an N-type diffusion layer formed in an island shape on the second surface of the high-resistance semiconductor substrate, and surrounding the N-type diffusion layer And a second gate electrode formed on the entire second surface of the high-resistance semiconductor substrate with a gate insulating film interposed therebetween.   A radiation detection apparatus comprising a plurality of radiation detectors according to any one of claims 1 to 4 stacked on top of each other.   A radiation detection apparatus comprising a plurality of radiation detectors according to claim 5 stacked one upon another.   7. The radiation detector according to claim 1, wherein an inversion layer exists under the gate electrode during a signal accumulation operation, and an inversion layer does not exist under the gate electrode during a signal read operation. A method of operating a radiation detector or a radiation detection apparatus, comprising:   8. The radiation detector according to claim 5, wherein an inversion layer exists under the first and second gate electrodes during the signal accumulation operation, and an inversion layer exists under the first and second gate electrodes during the signal readout operation. An operation method of a radiation detector or a radiation detection apparatus, wherein the operation is performed in a nonexistent state.

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