Patent Publication Number: US-2023138390-A1

Title: Optical sensor device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2019/000802, filed Jan. 11, 2019 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2018- 035701, filed Feb. 28, 2018, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an optical sensor device. 
     BACKGROUND 
     As an example of the optical sensor devices, the CMOS image sensor is conventionally known. The CMOS image sensor comprises a plurality of regions. The CMOS image sensor comprises a semiconductor layer formed of polycrystalline silicon. Since the CMOS image sensor is not suitable for lowering the definition or increasing the area of the regions, a further optical system needs to be used to condense light in the regions of the CMOS image sensor when used. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a circuit diagram showing an optical sensor device according to one embodiment. 
         FIG.  2    is an equivalent circuit diagram showing a region shown in  FIG.  1   , together with a control circuit, a power circuit and a selection switch, also shown in  FIG.  1   . 
         FIG.  3    is a plan view showing the region. 
         FIG.  4    is a cross-section showing the optical sensor device of  FIG.  3   , taken along a line IV-IV. 
         FIG.  5    is a cross-section showing the optical sensor device of  FIG.  3   , taken along a line V-V. 
         FIG.  6    is a cross-section showing the optical sensor device of  FIG.  3   , taken along a line VI-VI. 
         FIG.  7    is a timing chart showing signals applied to the above-described regions. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, there is provided an optical sensor device comprising an insulating substrate, an optical sensor element including a first gate electrode, a first semiconductor layer, a first electrode and a second electrode, a first insulating layer disposed between the first gate electrode and the first semiconductor layer, a second insulating layer disposed above the first gate electrode, the first semiconductor layer and the first insulating layer, a third insulating layer disposed on the second insulating layer, the first electrode and the second electrode, and a first conductive layer covering the optical sensor element. The first gate electrode is formed above the insulating substrate. The first semiconductor layer is formed of an oxide semiconductor and includes a first region, a second region and a first channel region located between the first region and the second region. The first channel region includes a first main surface opposing the first gate electrode and a second main surface at an opposite side of the first main surface. An electrical resistivity of the first channel region changes according to an amount of light received by the second main surface. The first electrode is located on the second insulating layer, and electrically connected to the first region through a first contact hole penetrating the second insulating layer and located in a region opposing the first region. The second electrode is located on the second insulating layer and electrically connected to the second region through a second contact hole penetrating the second insulating layer and located in a region opposing the second region. The first conductive layer is disposed above the third insulating layer and electrically connected to the second electrode through a third contact hole penetrating the third insulating layer and located in a region opposing the second electrode. 
     According to another embodiment, there is provided an optical sensor device comprising an insulating substrate, a first conductive layer disposed above the insulating substrate, and an optical sensor element disposed between the insulating substrate and the first conductive layer, electrically connected to the first conductive layer, covered by the first conductive layer, including a first semiconductor layer formed of an oxide semiconductor, and controlling an amount of charge flowing to the first conductive layer according to an amount of incident light. 
     According to another embodiment, there is provided an optical sensor device comprising an insulating substrate, and a plurality of regions arrayed in a matrix above the insulating substrate. Each of the plurality of regions comprises a first conductive layer disposed above the insulating substrate, and an optical sensor element disposed between the insulating substrate and the first conductive layer, electrically connected to the first conductive layer, covered by the first conductive layer, including a first semiconductor layer formed of an oxide semiconductor, and controlling an amount of charge flowing to the first conductive layer according to an amount of incident light to the first semiconductor layer. 
     An embodiment will be described hereinafter with reference to the accompanying drawings. The disclosure is merely an example, and proper changes within the spirit of the invention, which are easily conceivable by a skilled person, are included in the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same elements as those described in connection with preceding drawings are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary. 
       FIG.  1    is a circuit diagram showing an optical sensor device SD of an embodiment. A first direction X, a second direction Y and a third direction Z are orthogonal to each other, but may intersect at an angle other than 90°. The first direction X and the second direction Y correspond to the directions parallel to the main surface of a substrate which constitutes the optical sensor device SD, and the third direction Z corresponds to the thickness direction of the optical sensor device SD. 
     As shown in  FIG.  1   , the optical sensor device SD comprises an optical sensor panel SP, a control unit CN and a wiring substrate CB. The wiring substrate CB is, for example, a flexible printed circuit (FPC), and connects the control unit CN and the optical sensor panel SP to each other. The control unit CN includes a control circuit CC and a power circuit PO. 
     The optical sensor panel SP comprises an insulating substrate  10 , a plurality of regions PX, a plurality of gate lines G (G 1 , G 2 , ..., Gn), a plurality of source lines S (S 1 , S 2 , ..., Sm), and the like. The insulating substrate  10  is formed of an insulation material such as glass or resin. Further, in this embodiment, the insulating substrate  10  is formed of a transparent insulation material. The insulating substrate  10  comprises a detection area DA to detect an object and a non-detection area NDA of outside of the detection area DA. The non-detection area NDA includes a belt-shaped first non-detection area NDA 1  located on a left-hand side of the detection area DA and extending along the second direction Y, a belt-shaped second non-detection area NDA 2  located on a right-hand side of the detection area DA and extending along the second direction Y, a belt-shaped third non-detection area NDA 3  located on a lower side of the detection area DA and extending along the first direction X and a belt-shaped fourth non-detection area NDA 4  located on an upper side of the detection area DA and extending along the first direction X. A plurality of regions PX are disposed on the detection area DA of the insulating substrate  10  in a matrix along the first direction X and the second direction Y. 
     The plurality of gate lines G are arranged to extend in the first direction X and to be spaced apart from each other in the second direction Y in the detection area DA. Each gate line G is connected to a plurality of regions PX of one row in the first direction X. In this embodiment, a plurality of gate lines G of odd-numbered rows are each connected to lead wires L extending in the first non-detection area NDA 1  and the third non-detection area NDA 3 , respectively, on an outer side of the detection area DA. A plurality of gate lines G of even-numbered rows are connected to lead wires L extending in the second non-detection area NDA 2  and the third non-detection area NDA 3 , respectively, on an outer side of the detection area DA. Each lead wire L is connected to the wiring substrate CB. With the structure described above, each gate line G is connected to the control circuit CC via the respective lead wire L, the wiring substrate CB and the like. 
     A plurality of source lines S are arranged to extend along the second direction Y and to be spaced apart from each other along the first direction X in the detection area DA. Each source line S is connected to a plurality of regions PX of one column in the second direction Y. In this embodiment, each source line S is routed in the third non-detection area NDA 3  and connected to the wiring substrate CB outside the detection area DA. 
     Next, among the regions PX, one region PX will be described as a typical example. Note that these regions PX have configurations similar to each other.  FIG.  2    is an equivalent circuit showing a region PX shown in  FIG.  1   , illustrated along with a control circuit CC, a power circuit PO and a selection switch SS, shown in  FIG.  1   . 
     As seen in  FIG.  2   , the region PX comprises a optical sensor element SE, a capacitor CO, a reset switch RS and a control switch CS. On the insulating substrate  10  shown in  FIG.  1   , not only the gate lines G and the source lines S, but also a first control wiring line WL 1 , a second control wiring line WL 2 , a third control wiring line WL 3  and a fourth control wiring line WL 4  are also disposed. 
       FIG.  2    shows an example in which an optical sensor element SE is constituted by one first thin film transistor TR 1  for the sake of convenience. As will be described below, the optical sensor element SE of this embodiment is constituted by a plurality of first thin film transistors TR 1  connected in parallel with each other. Note that, the optical sensor element SE may be constituted by one first thin film transistor TR 1  unlike this embodiment. 
     The first thin film transistor TR 1  includes a first gate electrode GE 1 , a first electrode E 1  and a second electrode E 2 . The first gate electrode GE 1  is connected to the second control wiring line WL 2 , and the first electrode E 1  is connected to the first control wiring line WL 1 . The first thin film transistor TR 1  is turned on or off in reply to a control signal SVG to be applied via the second control wiring line WL 2 . 
     The capacitor CO includes a first conductive layer CL 1  and a second conductive layer CL 2 . The first conductive layer CL 1  is connected to the second electrode E 2 , and the second conductive layer CL 2  is connected to the third control wiring line WL 3 . 
     The reset switch RS is constituted by a second thin film transistor TR 2 . The second thin film transistor TR 2  includes a second gate electrode GE 2 , a third electrode E 3  and a fourth electrode E 4 . The second gate electrode GE 2  is connected to the fourth control wiring line WL 4 . The third electrode E 3  is connected to the third control wiring line WL 3  and the second conductive layer CL 2 . The fourth electrode E 4  is connected to the second electrode E 2  and the first conductive layer CL 1 . The second thin film transistor TR 2  is turned on or off in reply to the control signal DCH to be applied via the fourth control wiring line WL 4 . 
     The control switch CS is constituted by the third thin film transistor TR 3 . The third thin film transistor TR 3  includes a third gate electrode GE 3 , a fifth electrode E 5  and a sixth electrode E 6 . The third gate electrode GE 3  is connected to a gate line G, and the fifth electrode E 5  is connected to a source line S. The sixth electrode E 6  is connected to the second electrode E 2 , the fourth electrode E 4  and the first conductive layer CL 1 . The third thin film transistor TR 3  is turned on or off in reply to a control signal Gate to be applied via the respective gate line G. 
     The control unit CN also includes the selection switch SS and the fifth control wiring line WL 5  as well in addition to the control circuit CC and the power circuit PO. The selection switch SS includes a fourth thin film transistor TR 4  and a fifth thin film transistor TR 5 . In this embodiment, the first thin film transistor TR 1  to the fourth thin film transistor TR 4  are N-channel thin-film transistors, whereas the fifth thin film transistor TR 5  is a P-channel thin-film transistor. 
     The fourth thin film transistor TR 4  is connected between the source line S and the power circuit PO. The fifth thin film transistor TR 5  is connected between the source line S and the control circuit CC. The fourth thin film transistor TR 4  and the fifth thin film transistor TR 5  are turned on or off according to control signals RST to be applied via the fifth control wiring line WL 5 , respectively. 
     When the fourth thin film transistor TR 4  is on and the fifth thin film transistor TR 5  is off, the selection switch SS applies a reset signal VR 1  to the optical sensor element SE from the power circuit PO via the source line S and the control switch CS. On the other hand, when the fourth thin film transistor TR 4  is off whereas the fifth thin film transistor TR 5  is on, the selection switch SS opens to discharge from the capacitor CO to the control circuit CC via the control switch CS and the source line S. Thus, a current I flows to the control circuit CC from the capacitor CO. 
     When the optical sensor element SE is turned on, the optical sensor element SE is reset by a reset signal VR 1  to be applied via the control switch CS. On the other hand, when the optical sensor element SE is off, the optical sensor element SE controls the amount of charge flowing to the first conductive layer CL 1  according to the amount of the incident light to the first semiconductor layers SMC 1 . In other words, the optical sensor element SE control the amount of the portion of the control signal SVS applied via the first control wiring line WL 1  to the first electrode E 1 , which is applied to the first conductive layer CL 1 , according to the amount of the incident light to the first semiconductor layers SMC 1 . Thus, the optical sensor element SE controls the amount of charge stored on the capacitor CO according to the amount of the incident light to the first semiconductor layers SMC 1 . 
     When the reset switch RS is turned on, the reset switch RS connects the first conductive layer CL 1  and the second conductive layer CL 2  to short-circuit. Note that to the third electrode E 3  of the reset switch RS, the reset signal VR 1  is applied. The reset signal VR 1  is a constant-potential voltage signal. When the reset switch RS is off, the reset switch RS maintains an original function of the capacitor CO. Thus, the capacitor CO is reset when the reset switch RS is turned on. 
     When the control switch CS is turned on, the control switch CS switches between whether or not the reset signal VR 1  is applied to the optical sensor element SE. Further, when the control switch CS is turned on, the control switch CS switches between whether or not to discharge from the capacitor CO to the control circuit CC. 
       FIG.  3    is a plan view showing a region PX shown in  FIG.  2   . Note that, in  FIG.  3   , the illustration of the second conductive layer CL 2  is omitted. 
     As shown in  FIG.  3   , the first conductive layer CL 1  (the capacitor CO) covers the optical sensor element SE, the reset switch RS and the control switch CS. The first conductive layer CL 1  functions as a common node of the optical sensor element SE, the reset switch RS and the control switch CS. Therefore, as compared to the case where the first conductive layer CL 1  does not function as the node, the area efficiency of the optical sensor element SE, the reset switch RS and the control switch CS in the region PX can be improved. For example, the wiring to connect the optical sensor element SE, the reset switch RS and the control switch CS to each other can be reduced, and the area where the optical sensor element SE or the like is to be placed can be largely reserved. 
     Of the optical sensor element SE, the reset switch RS and the control switch CS, the area exclusively occupied by the optical sensor element SE is the largest. For example, the optical sensor element SE occupies 50% or more of the range opposing to the first conductive layer CL 1 . Therefore, a high-sensitivity optical sensor element SE can be obtained. 
     The optical sensor element SE includes stripe-shaped first electrodes E 1  which extend, for example, in the second direction Y and are arranged to be spaced apart from each other in the first direction X. The first electrodes E 1  are electrically bundled and are connected to the first control wiring line WL 1 . In this embodiment, the first electrode E 1  and the first control wiring line WL 1  are formed integrally as one body. 
     The optical sensor element SE includes a plurality of second electrodes E 2 . The second electrodes E 2  each extend in the second direction Y and are each located between respective adjacent pair of first electrodes E 1 . In the example illustrated, an upper-side second electrode E 2  and a lower-side second electrode E 2  are located apart from each other by an insulation distance, in a region between a respective adjacent pair of first electrodes E 1 . The second electrodes E 2  are each connected to the first conductive layer CL 1 . In the example illustrated, the optical sensor element SE comprise twenty four first thin film transistors TR 1  connected in parallel. 
     The optical sensor element SE includes stripe-shaped first gate electrodes GE 1  which extend, for example, in the second direction Y and are arranged to be spaced apart from each other in the first direction X. The first gate electrodes GE 1  are electrically bundled and are connected to the second control wiring line WL 2 . 
     The optical sensor element SE includes, for example, a plurality of first semiconductor layers SMC 1 . As viewed along the second direction Y, two first semiconductor layers SMC 1  are arranged to be physically independent from each other. Note here that three or more first semiconductor layers SMC 1  may be arranged to be physically independent from each other in the second direction Y, or a single first semiconductor layer SMC 1  may extend continually in the second direction Y, unlike the present embodiment. In other words, the first semiconductor layer SMC 1  need not necessarily be divided into multiple in the second direction Y. 
     In the reset switch RS, the third electrode E 3  extends, for example, in the first direction X, and is formed to be integrated as one body with the third control wiring line WL 3  extending in the second direction Y. The fourth electrode E 4  extends, for example, in the first direction X and is connected to the first conductive layer CL 1 . The second gate electrode GE 2  extends in the first direction X so as to be located between the third electrode E 3  and the fourth electrode E 4 , and is electrically connected to the fourth control wiring line WL 4  extending in the second direction Y. A first light-shielding layer SH 1  is provided to oppose the second gate electrode GE 2  and extend along the second gate electrode GE 2 . 
     In the control switch CS, the fifth electrode E 5  extends, for example, in the second direction Y and is formed to be integrated as one body with the source line S extending in the second direction Y. The sixth electrode E 6  extends, for example, in the second direction Y and is connected to the first conductive layer CL 1 . The third gate electrode GE 3  extends in the second direction Y so as to be located between the fifth electrode E 5  and the sixth electrode E 6  and is formed to be integrated as one body with the respective gate line G extending in the first direction X. A second light-shielding layer SH 2  is provided to oppose the third gate electrode GE 3  and extend along the third gate electrode GE 3 . 
     The third semiconductor layer SMC 3  of the control switch CS extends continually in the second direction Y. Note here that the control switch CS may include a plurality of third semiconductor layers SMC 3  arranged to be physically independent from each other in the second direction Y, unlike the present embodiment. 
     The first light-shielding layer SH 1  and the second light-shielding layer SH 2  are formed of the same material. The gate lines G, the first gate electrode GE 1 , the second gate electrode GE 2  and the third gate electrode GE 3  are formed of the same material. The first electrode E 1  to the sixth electrode E 6 , the source lines S and the first control wiring line WL 1  to the fourth control wiring line WL 4  are formed of the same material. 
     Next, a cross-sectional structure of each of the optical sensor element SE and the capacitor CO will be described.  FIG.  4    is a cross-section of the optical sensor device SD shown in  FIG.  3   , taken along a line IV-IV. 
     As shown in  FIG.  4   , a glass substrate can be used as the insulating substrate  10 . Note that some other substrate than the glass substrate may be used for the insulating substrate  10 . For example, the insulating substrate  10  may be a resin substrate. Further, the insulating substrate  10  may be light-transmissive as needed. Above the insulating substrate  10 , the optical sensor element SE including the first gate electrode GE 1 , the first semiconductor layer SMC 1 , the first electrode E 1  and the second electrode E 2 , is located. The optical sensor element SE is constituted by a plurality of first thin film transistors TR 1 , and each of the first thin film transistors TR 1  includes the first gate electrode GE 1 , the first semiconductor layer SMC 1 , the first electrode E 1  and the second electrode E 2 . Above the optical sensor element SE, the capacitor CO including the first conductive layer CL 1  and the second conductive layer CL 2  is located. 
     The insulating layer  11  is disposed on the insulating substrate  10  and is in contact with the insulating substrate  10 . The insulating layer  12  is disposed on the insulating layer  11  and is in contact with the insulating layer  11 . The first gate electrode GE 1  is disposed above the insulating substrate  10 . The insulating layer  13  is disposed between the first gate electrode GE 1  and the first semiconductor layer SMC 1 . The insulating layer  14  is disposed above the first gate electrode GE 1 , the first semiconductor layer SMC 1  and the first insulating layer  13 . The insulating layer  15  is disposed on the insulating layer  14 , the first electrode E 1  and the second electrode E 2 . 
     The first semiconductor layer SMC 1  is formed of an oxide semiconductor. Typical examples of the oxide semiconductor are indium-gallium-zinc oxide (IGZO), indium-gallium oxide (IGO), indium-zinc oxide (IZO), zinc-tin oxide (ZnSnO), zinc oxide (ZnO) and transparent amorphous oxide semiconductor (TAOS). In this embodiment, the first semiconductor layer SMC 1  is formed of TAOS. 
     When an oxide semiconductor as described above is used, the first thin film transistor TR 1  can suppress the current (leak current) in a dark condition to low, thereby achieving a great signal-to-noise ratio. 
     The first semiconductor layer SMC 1  includes a first region R 1 , a second region R 2  and a first channel region RC 1  located between the first region R 1  and second region R 2 . The first channel region RC 1  includes a first main surface SU 1  opposing the first gate electrode GE 1  and a second main surface SU 2  at an opposite side of the first main surface SU 1 . The first channel region RC 1  changes its electrical resistivity according to the amount of light received by the second main surface SU 2 . 
     The second main surface SU 2  of this embodiment is located to oppose the insulating substrate  10 . On the second main surface SU 2 , the light transmitted through the insulating substrate  10  is made incident. Therefore, the insulating substrate  10  of the embodiment is light-transmissive. 
     The first electrode E 1  is disposed on the insulating layer  14 . The first electrode E 1  passes through a first contact hole CH 1  formed to penetrate at least the insulating layer  14  and located in a region opposing the first region R 1 , and is electrically connected to the first region R 1 . In this embodiment, the first contact hole CH 1  penetrates the insulating layer  13  and the insulating layer  14 . 
     The second electrode E 2  is disposed on the insulating layer  14 . The second electrode E 2  passes through a second contact hole CH 2  formed to penetrate at least the insulating layer  14  and located in a region opposing the second region R 2 , and is electrically connected to the second region R 2 . In this embodiment, the second contact hole CH 2  penetrates the insulating layer  13  and the insulating layer  14 . 
     The first conductive layer CL 1  is disposed above the insulating layer  15  so as to cover the optical sensor element SE. In this embodiment, the first conductive layer CL 1  is in contact with the insulating layer  15 . The first conductive layer CL 1  passes through a third contact hole CH 3  formed to penetrate at least the insulating layer  15  and located in a region opposing the second electrode E 2 , and is electrically connected to the second electrode E 2 . In this embodiment, the third contact hole CH 3  penetrates only the insulating layer  15 . 
     Note that in the insulating layer  15 , a plurality of holes similarly configured as the third contact hole CH 3  are formed (see  FIG.  3   ). The number of the third contact holes CH 3  is equal to or more than the number of the second electrodes E 2 . With the above-described structure, the first conductive layer CL 1  passes through a corresponding one of the third contact holes CH 3 , and is electrically connected to the second electrode E 2  of each of the first thin film transistors TR 1 . 
     The insulating layer  16  is disposed on the insulating layer  15  and the first conductive layer CL 1 , and is in contact with the insulating layer  15  and the first conductive layer CL 1 . The second conductive layer CL 2  opposes the first conductive layer CL 1 . Though not illustrated entirely, the second conductive layer CL 2  opposes a plurality of first conductive layers CL 1 . Note that the insulating layer  16  is disposed between the first conductive layer CL 1  and the second conductive layer CL 2 . The first conductive layer CL 1  is disposed between the insulating layer  15  and the second conductive layer CL 2 . With this structure, the second conductive layer CL 2  can avoid such a situation that the first conductive layer CL 1  is affected by an adverse electrical effect from outside such as static electricity or the like. 
     The insulating layer  17  is disposed on the insulating layer  16  and the second conductive layer CL 2 , and is in contact with the insulating layer  16  and the second conductive layer CL 2 . 
     The first gate electrode GE 1 , the first electrode E 1  and the second electrode E 2  are formed of, for example, molybdenum, chrome, tungsten, aluminum, copper, titanium, nickel, tantalum, silver or an alloy of any of these, but the material is not limited to those listed. Some other metals, alloys or laminated films thereof may as well be used. 
     The first conductive layer CL 1  and the second conductive layer CL 2  are formed of a light-transmissive conductive material such as ITO or the like. Therefore, the optical sensor panel SP can be formed by a production method similar to that of the fringe field switching (FFS) mode liquid-crystal display panel. Note that the first conductive layer CL 1  and the second conductive layer CL 2  may be formed of a light-shielding conductive material such as a metal or the like. This is because the optical sensor element SE is to detect the light transmitted through the insulating substrate  10 . 
     The insulating layer  11 , insulating layer  12 , insulating layer  13 , insulating layer  14  and insulating layer  16  are formed of an inorganic insulating layer of silicon oxide or silicon nitride or the like, or a multi-layer thereof. The insulating layer  15  and the insulating layer  17  are formed from an organic insulating layer. 
     Next, a cross-sectional structure of each of the reset switch RS and the capacitor CO will be described.  FIG.  5    is a cross-section of the optical sensor device SD shown in  FIG.  3   , taken along a line V-V. 
     As shown in  FIG.  5   , above the insulating substrate  10 , the reset switch RS including the second gate electrode GE 2 , the second semiconductor layer SMC 2 , the third electrode E 3  and the fourth electrode E 4  is located. The reset switch RS is constituted by the second thin film transistor TR 2 . Above the reset switch RS, the capacitor CO is located. 
     The insulating layer  12  is located between the first light-shielding layer SH 1  and the second semiconductor layer SMC 2 . The second gate electrode GE 2  is formed above the insulating substrate  10 . The second semiconductor layer SMC 2  is formed of, for example, TAOS as an oxide semiconductor. The second semiconductor layer SMC 2  includes a third region R 3 , a fourth region R 4  and a second channel region RC 2  located between the third region R 3  and the fourth region R 4 . The second channel region RC 2  includes a third main surface SU 3  opposing the second gate electrode GE 2  and a fourth main surface SU 4  located at an opposite side of the third main surface SU 3  and opposing the first light-shielding layer SH 1 . 
     The insulating layer  13  is further disposed between the second gate electrode GE 2  and the second semiconductor layer SMC 2 . The insulating layer  14  is further disposed above the first light-shielding layer SH 1 , the second gate electrode GE 2  and the second semiconductor layer SMC 2 . 
     The third electrode E 3  is disposed on the insulating layer  14 . The third electrode E 3  passes through a fourth contact hole CH 4  penetrating at least the insulating layer  14  and located in a region opposing the third region R 3 , and is electrically connected to the third region R 3 . In the embodiment, the fourth contact hole CH 4  penetrates the insulating layer  13  and the insulating layer  14 . 
     The fourth electrode E 4  is disposed on the insulating layer  14 . The fourth electrode E 4  passes through a fifth contact hole CH 5  penetrating at least the insulating layer  14  and located in a region opposing the fourth region R 4 , and is electrically connected to the fourth region R 4 . In the embodiment, the fifth contact hole CH 5  penetrates the insulating layer  13  and the insulating layer  14 . 
     The first conductive layer CL 1  covers the reset switch RS. The first conductive layer CL 1  passes through a sixth contact hole CH 6  penetrating at least the insulating layer  15  and located in a region opposing the fourth electrode E 4 , and is electrically connected to the fourth electrode E 4 . In the embodiment, the sixth contact hole CH 6  penetrates only the insulating layer  15 . 
     The second conductive layer CL 2  passes through a seventh contact hole CH 7  penetrating at least the insulating layer  15  and located in a region opposing the third electrode E 3 , and is electrically connected to the third electrode E 3 . In the embodiment, the seventh contact hole CH 7  penetrates the insulating layer  15  and the insulating layer  16 . Note that the first conductive layer CL 1  comprises an opening OP which surrounds the seventh contact hole CH 7 . 
     Next, a cross-sectional structure of each of the control switch CS and the capacitor CO will be described.  FIG.  6    is a cross-section of the optical sensor device SD shown in  FIG.  3   , taken along a line VI-VI. 
     As shown in  FIG.  6   , above the insulating substrate  10 , the control switch CS including the third gate electrode GE 3 , the third semiconductor layer SMC 3 , the fifth electrode E 5  and the sixth electrode E 6 , is located. The control switch CS is constituted by the third thin film transistor TR 3 . Above the control switch CS, the capacitor CO is located. 
     The insulating layer  12  is further disposed between the second light-shielding layer SH 2  and the third semiconductor layer SMC 3 . The third gate electrode GE 3  is disposed above the insulating substrate  10 . The third semiconductor layer SMC 3  is formed of, for example, TAOS as an oxide semiconductor. The third semiconductor layer SMC 3  includes a fifth region R 5 , a sixth region R 6  and a third channel region RC 3  located between the fifth region R 5  and the sixth region R 6 . The third channel region RC 3  includes a fifth main surface SU 5  opposing the third gate electrode GE 3  and a sixth main surface SU 6  located at an opposite side of the fifth main surface SU 5  and opposing the second light-shielding layer SH 2 . 
     The insulating layer  13  is further disposed between the third gate electrode GE 3  and the third semiconductor layer SMC 3 . The insulating layer  14  is further disposed above the second light-shielding layer SH 2 , the third gate electrode GE 3  and the third semiconductor layer SMC 3 . 
     The fifth electrode E 5  is disposed on the insulating layer  14 . The fifth electrode E 5  passes through an eighth contact hole CH 8  penetrating at least the insulating layer  14  and located in a region opposing the fifth region R 5 , and is electrically connected to the fifth region R 5 . In the embodiment, the eighth contact hole CH 8  penetrates the insulating layer  13  and the insulating layer  14 . 
     The sixth electrode E 6  is disposed on the insulating layer  14 . The sixth electrode E 6  passes through a ninth contact hole CH 9  penetrating at least the insulating layer  14  and located in a region opposing the sixth region R 6 , and is electrically connected to the sixth region R 6 . In the embodiment, the ninth contact hole CH 9  penetrate the insulating layer  13  and the insulating layer  14 . 
     The first conductive layer CL 1  covers the control switch CS. The first conductive layer CL 1  passes through a tenth contact hole CH 10  penetrating at least the insulating layer  15  and located in a region opposing the sixth electrode E 6 , and is electrically connected to the sixth electrode E 6 . In the embodiment, the tenth contact hole CH 10  penetrates only the insulating layer  15 . 
     The optical sensor device SD of the embodiment is configured as described above. 
     Next, a method of driving the optical sensor device SD of the embodiment will be described by illustrating an example thereof.  FIG.  7    is a timing chart showing signals to be applied to the regions PX, respectively. 
     As shown in  FIGS.  7  and  2   , a period in which detection operation to detect an object in the detection area DA of the optical sensor panel SP is carried out once is defined as a detection period Pd. The detection period Pd includes a first transition period P t   1 , a first reset period P r   1 , a second transition period P t   2 , a second reset period P r   2 , an exposure period Pe, a third transition period P t   3  and a read period Pa. 
     First, in the first transition period P t   1 , the control unit CN switches the level of the control signal SVS from an H (high) level to an L (low) level and the level of the control signal SVG from the L level to the H level. Thus, in the first transition period P t   1 , the first electrode E 1  of the optical sensor element SE changes to an L level (-1 V) and the first gate electrode GE 1  changes to an H level (10 V). Note that the voltage value used in the embodiment is only an example and can be modified in various ways. 
     Subsequently, when shifted to the first reset period P r   1 , the control unit CN applies control signals Gate ( 1 ), ..., Gate (n) of an H level (10 V) respectively to the gate lines G, and then switches the level of the control signals Gate ( 1 ), ..., Gate (n), from the H level to an L level (-5 V). The first reset period P r   1  includes a period after the level of the control signals Gate was switched from the H level to the L level, and therefore the potential of the third gate electrode GE 3  of the control switch CS can be changed to substantially 10 V. 
     In the embodiment, a plurality of gate lines G are driven for time division. More specifically, the level of the control signal Gate ( 1 ) applied to the gate line G 1  is switched from the H level to the L level, and thereafter the level of the control signal Gate applied to the gate line G 2  is switched from the L level to the H level. Then, the level of the control signal Gate applied to the gate line G 2  is switched from the H level to the L level, and thereafter, the level of the control signal Gate applied to the gate line G 3  is switched from the L level to the H level. Lastly, the level of the control signal Gate (n) applied to the gate line Gn is switched from the H level to the L level. 
     When the control signal Gate of the H level is applied via the respective gate line G corresponding to the respective one of the control switch CS, the control switch CS is turned on to apply a reset signal VR 1  output from the power circuit PO via the respective selection switch SS and the respective source line S, to the optical sensor device SE. The control unit CN applies the reset signal VR 1  to the optical sensor element SE from the power circuit PO via the source line S and the control switch CS. As the reset signal VR 1  flows from the second electrode E 2  of the optical sensor element SE to the first electrode E 1  of the optical sensor element SE, the optical sensor device SE is reset. 
     After that, when shifted to the second transition period P t   2 , the control unit CN switches the level of the control signal SVG from the H level to the L level. Thus, in the second transition period P t   2 , the first gate electrode GE 1  of the optical sensor element SE is changed to the L level, thereby turning off the optical sensor element SE. 
     Subsequently, when shifted to the second reset period P r   2 , the control unit CN switches the level of the control signal DCH from an L level (-5 V) to an H level (10 V), and also the level of the control signal SVS from an L level to an H level. Thus, the reset switch RS is turned on to apply the reset signal VR 1  to the first conductive layer CL 1  and the second conductive layer CL 2  via the third control wiring line WL 3 , thereby resetting the capacitor CO. 
     Next, when shifted to the exposure period Pe, the control unit CN switches the level of the control signal DCH from the H level to the L level. Thus, the reset switch RS is turned off. The optical sensor element SE controls the amount of the control signal SVS of the H level applied to the first electrode E 1  via the first control wiring line WL 1 , to the first conductive layer CL 1  according to the amount of the incident light to the first semiconductor layers SMC 1 . Here, the greater the amount of light made incident on the optical sensor element SE, the greater the amount of charge stored on the capacitor CO. Note that second semiconductor layer SMC 2  of the reset switch RS is light-shielded by the first light-shielding layer SH 1  and the third semiconductor layer SMC 3  of the control switch CS is light-shielded by the second light-shielding layer SH 2 . Therefore, the reset switch RS and the control switch CS are in a dark condition at all times. 
     After that, when shifted to the third transition period P t   3 , the control unit CN switches the level of the control signal RST from an H level (10 V) to an L level (-5 V). Thus, in the third transition period P t   3 , the fourth thin film transistor TR 4  is switched to an off state and the fifth thin film transistor TR 5  is switched to an on state. 
     Then, when shifted to the read period Pa, the control unit CN, after applying the control signals Gate ( 1 ), ..., Gate (n) of the H level to the respective gate lines G, switches the level of the control signals Gate( 1 ), ..., Gate (n) from the H level to the L level. Here, the read period Pa includes a period after the level of the control signals Gate is switched to the L level from the H level, the potential of the third gate electrode GE 3  of the control switch CS is changed to substantially10 V. 
     The read period Pa of the embodiment, a plurality of gate lines G are driven by time division. When the control signals Gate of the H level are applied via the gate lines G corresponding to the respective control switches CS, the control switches CS are turned on. Thus, the capacitors CO discharge to the control circuit CC. Here, a current I flows to the control circuit CC from each capacitor CO. Note that in the read period Pa, a plurality of gate line G may be driven in a batch at the same time. Thus, the read period Pa can be shortened. 
     According to the optical sensor device SD of the embodiment, configured as described above, the optical sensor device SD comprises the insulating substrate  10 , the regions PX arrayed in a matrix on the insulating substrate  10  and the first conductive layer CL 1 . The regions PX each comprises an optical sensor element SE, a reset switch RS and a control switch CS. 
     The optical sensor element SE, the reset switch RS and the control switch CS are each connected to the first conductive layer CL 1  and they are covered by the first conductive layer CL 1 . With this configuration, the area for placing the optical sensor element SE, the reset switch RS and the control switch CS in the region PX can be increased. 
     The second conductive layer CL 2  covers the first conductive layer CL 1 . Therefore, the capacitor CO can be formed using the first conductive layer CL 1  and the second conductive layer CL 2 . The second conductive layer CL 2  can avoid such a situation that the first conductive layer CL 1  is affected by an adverse electrical effect from outside such as static electricity or the like. 
     As described above, a high-sensitivity optical sensor device SD can be obtained. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     For example, the thin film transistor TR such as the first thin film transistor TR 1  may not be a top-gate thin-film transistor, but a bottom-gate thin-film transistor. In this case, the second main surface SU 2  of the first channel region RC 1  of the first semiconductor layer SMC 1  opposes the first conductive layer CL 1 . On the second main surface SU 2 , light transmitted through the first conductive layer CL 1  and the like is made incident. The first conductive layer CL 1  and the second conductive layer CL 2  are light-transmissive, but the insulating substrate  10  need not necessarily be light-transmissive. 
     The locations of the first conductive layer CL 1  and the second conductive layer CL 2  in relation to each other may be reverse to that of the embodiment. In this case, the second conductive layer CL 2  is located between the insulating substrate  10  and the first conductive layer CL 1 . In this case, the first conductive layer CL 1  does not comprise an opening OP, and the second conductive layer CL 2  comprises an opening to connect the first conductive layer CL 1  to the third electrode E 3  (the third control wiring line WL 3 ) . 
     The first light-shielding layer SH 1  and the second light-shielding layer SH 2  may be formed of an insulation material such as black resin or formed of a conductive material such a metal. When the light-shielding layer SH is formed of a metal, the light-shielding layer SH may be electrically floated. Or, the control signals Gate may be applied to the light-shielding layer SH as well to utilize the light-shielding layer SH as a gate electrode.