Patent EA-003343-B1 (EA)
Title: Photosensor and photosensor system
Inventor: SASAKI KAZUHIRO
IPC: H01L27/146
Filed: 2000-07-28
Abstract: 1. A photosensor comprising: a first gate electrode; a first gate insulating film provided above said first gate electrode; at least one semiconductor layer provided above said first gate insulating film; source and drain electrodes for causing drain current to flow in said semiconductor layer; a second gate insulating film provided above said semiconductor layer; and a second gate electrode provided above said second gate insulating film, characterized in that said semiconductor layer includes a plurality of channel regions in which drain current flows. 2. The photosensor according to claim 1, characterized in that said channel regions are arranged side by side in the direction of a channel length of said semiconductor layer. 3. The photosensor according to claim 1, characterized in that one of said source and drain electrodes is formed so as to extend over said channel regions. 4. The photosensor according to claim 1, characterized in that said semiconductor layer is divided into plural semiconductor layer sections and each of said plural semiconductor layer sections has one of said channel regions. 5. The photosensor according to claim 1, characterized in that said semiconductor layer is divided into plural semiconductor layer sections and each of said plural semiconductor layer sections has two or more of said channel regions. 6. The photosensor according to claim 1, characterized in that said semiconductor layer has a plurality of carrier generating regions. 7. The photosensor according to claim 1, characterized in that said semiconductor layer is divided into plural semiconductor layer sections and each of said plural semiconductor layer sections has one of carrier generating regions. 8. The photosensor according to claim 7, characterized in that said carrier generating regions are arranged side by side in the direction of the channel length of said semiconductor layer. 9. The photosensor according to claim 1, characterized in that said semiconductor layer is divided into plural semiconductor layer sections and each of said plural semiconductor layer sections has two or more of said carrier generating regions. 10. The photosensor according to claim 9, characterized in that said carrier generating regions are arranged side by side in the direction of the channel length of said semiconductor layer. 11. The photosensor according to claim 1, characterized in that at least either said source or drain electrodes are plural. 12. The photosensor according to claim 1, characterized in that semiconductor layer is divided into plural semiconductor layer sections and one of said source and drain electrodes are formed so as to extend over said plural semiconductor layer sections. 13. The photosensor according to claim 1, characterized in that said source and drain electrodes are made of material that shuts off exciting light. 14. The photosensor according to claim 1, characterized by further comprising impurity doped layers each intervening between said semiconductor layer and said source and drain electrodes. 15. The photosensor according to claim 1, characterized by further comprising a block insulating layer intervening between said semiconductor layer and said second gate insulating film. 16. The photosensor according to claim 1, characterized in that said second gate electrode is made of material that allows said exciting light to pass through. 17. A photosensor system characterized by comprising: (a) photosensors according to claim 1 arranged in a matrix, (b) source lines connected to the source electrodes of said photosensors arranged in a first direction; (c) drain lines connected to the drain electrodes of said photosensors arranged in said first direction; (d) first gate lines connected to the first gate electrodes of said photosensors arranged in a second direction; (e) second gate lines connected to the second gate electrodes of said photosensors arranged in said second direction; (f) precharging means for outputting a precharge voltage to said drain lines; (g) reading means to which a precharge voltage varied according to the incident light on said photosensors is inputted; (h) a first gate driver for supplying a signal to said first gate lines; and (i) a second gate driver for supplying a signal to said second gate lines. 18. The photosensor system according to claim 17, characterized in that said first gate driver outputs a signal for selectively bringing said photosensors into one of a selection state and a non-selection state. 19. The photosensor system according to claim 17, characterized in that said second gate driver outputs a signal for selectively bringing said photosensors into one of a reset state and a carrier accumulated state. 20. The photosensor system according to claim 17, characterized by further comprising a light source for emitting light including said exciting light. 21. The photosensor according to claim 1, characterized in that a semiconductor layer comprises carrier generating regions for generating carriers by incident exciting light.