Semiconductor device and driving method thereof
First Claim
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1. A semiconductor device comprising a pixel circuit comprising a plurality of pixels, each of the plurality of pixels comprising:
- a display element; and
a photosensor,wherein the photosensor comprises;
a photodiode;
a first transistor having a stacked structure including a gate, a gate insulating layer, a semiconductor layer, an insulating film, and a back gate; and
a second transistor comprising a gate, a first terminal, and a second terminal,wherein the photodiode is electrically connected to the first terminal of the second transistor, andwherein the second terminal of the second transistor is electrically connected to the gate of the first transistor.
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Abstract
A semiconductor device including photosensor capable of imaging with high resolution is disclosed. The semiconductor device includes the photosensor having a photodiode, a first transistor, and a second transistor. The photodiode generates an electric signal in accordance with the intensity of light. The first transistor stores charge in a gate thereof and converts the stored charge into an output signal. The second transistor transfers the electric signal generated by the photodiode to the gate of the first transistor and holds the charge stored in the gate of the first transistor. The first transistor has a back gate and the threshold voltage thereof is changed by changing the potential of the back gate.
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Citations
20 Claims
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1. A semiconductor device comprising a pixel circuit comprising a plurality of pixels, each of the plurality of pixels comprising:
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a display element; and a photosensor, wherein the photosensor comprises; a photodiode; a first transistor having a stacked structure including a gate, a gate insulating layer, a semiconductor layer, an insulating film, and a back gate; and a second transistor comprising a gate, a first terminal, and a second terminal, wherein the photodiode is electrically connected to the first terminal of the second transistor, and wherein the second terminal of the second transistor is electrically connected to the gate of the first transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A semiconductor device comprising a pixel circuit comprising a plurality of pixels, each of the plurality of pixels comprising:
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a display element; and a photosensor, wherein the photosensor comprises; a photodiode comprising a pair of electrodes with a semiconductor interposed between the pair of electrodes; a first transistor having a stacked structure including a gate, a gate insulating layer, a semiconductor layer, an insulating film, and a back gate, the gate insulating layer and the semiconductor layer being interposed between the gate and the back gate; and a second transistor comprising; a second gate; a gate insulating layer over the second gate; a semiconductor layer over the gate insulating layer; a first terminal and a second terminal over the semiconductor layer; and an oxide insulating layer over and in contact with the first terminal, the second terminal, and the semiconductor layer of the second transistor, wherein one of the pair of electrodes is electrically connected to one of the first terminal and the second terminal, and wherein the other of the first terminal and the second terminal is electrically connected to the gate of the first transistor. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A driving method of a semiconductor device comprising a plurality of pixels each of which comprises a display element and a photosensor, the driving method comprising the steps of:
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transferring an electric signal generated by a photodiode to a gate of a first transistor through a second transistor which is in a conduction state, keeping a back gate of the first transistor at a first potential, wherein the photodiode, the first transistor, and the second transistor are included in the photosensor; holding charge stored in the gate by turning the second transistor to a non-conduction state; converting the charge stored in the gate of the first transistor to a first output signal; providing a second potential to the back gate, wherein the second potential is different from the first potential; and converting the charge stored in the gate to a second output signal, while keeping the back gate at the second potential, wherein the back gate is provided over the gate with a semiconductor layer therebetween. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification
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Current AssigneeSemiconductor Energy Laboratory Co., Ltd.
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Original AssigneeSemiconductor Energy Laboratory Co., Ltd.
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InventorsKurokawa, Yoshiyuki
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Primary Examiner(s)Epps, Georgia Y
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Assistant Examiner(s)WILLIAMS, DON J
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Application NumberUS13/021,144Publication NumberTime in Patent Office1,019 DaysField of Search250/214.R, 250/214.1, 250/208.1, 345 4- 6, 345 38- 40, 345 44- 46, 345/50, 345/51, 345/55, 345/84, 345/90, 345/104, 349/140, 349/151US Class Current250/214.RCPC Class CodesG01J 1/44 Electric circuits for comma...G01J 2001/4446 Type of detectorH01L 27/1225 with semiconductor material...H01L 27/14609 Pixel-elements with integra...H01L 27/14614 having a special gate struc...H01L 27/14616 characterised by the channe...H01L 29/7869 having a semiconductor body...H01L 31/032 including, apart from dopin...H04N 23/68 for stable pick-up of the s...H04N 25/00 Circuitry of solid-state im...H04N 25/76 Addressed sensors, e.g. MOS...
