Semiconductor device including photosensor and transistor having oxide semiconductor active layer
First Claim
1. A semiconductor device comprising:
- a photosensor comprising;
a photodiode;
a first transistor having a gate, the gate of the first transistor being electrically connected to one electrode of the photodiode;
a second transistor having a source and a drain, one of the source and the drain of the second transistor being connected to one of a source and a drain of the first transistor; and
a read control circuit including a read control transistor having a source and a drain, one of the source and the drain of the read control transistor being connected to the other of the source and the drain of the first transistor,wherein the other of the source and the drain of the read control transistor is connected to a first wiring which is configured to be supplied with a first reference potential,wherein the other of the source and the drain of the second transistor is connected to a second wiring which is configured to be supplied with a second reference potential,wherein the second reference potential is lower than the first reference potential, andwherein the read control transistor has a channel formation region comprising an oxide semiconductor.
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Abstract
An object is to achieve low-power consumption by reducing the off-state current of a transistor in a photosensor. A semiconductor device including a photosensor having a photodiode, a first transistor, and a second transistor; and a read control circuit including a read control transistor, in which the photodiode has a function of supplying charge based on incident light to a gate of the first transistor; the first transistor has a function of storing charge supplied to its gate and converting the charge stored into an output signal; the second transistor has a function of controlling reading of the output signal; the read control transistor functions as a resistor converting the output signal into a voltage signal; and semiconductor layers of the first transistor, the second transistor, and the read control transistor are formed using an oxide semiconductor.
137 Citations
20 Claims
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1. A semiconductor device comprising:
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a photosensor comprising; a photodiode; a first transistor having a gate, the gate of the first transistor being electrically connected to one electrode of the photodiode; a second transistor having a source and a drain, one of the source and the drain of the second transistor being connected to one of a source and a drain of the first transistor; and a read control circuit including a read control transistor having a source and a drain, one of the source and the drain of the read control transistor being connected to the other of the source and the drain of the first transistor, wherein the other of the source and the drain of the read control transistor is connected to a first wiring which is configured to be supplied with a first reference potential, wherein the other of the source and the drain of the second transistor is connected to a second wiring which is configured to be supplied with a second reference potential, wherein the second reference potential is lower than the first reference potential, and wherein the read control transistor has a channel formation region comprising an oxide semiconductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A semiconductor device comprising:
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a photosensor comprising; a photodiode comprising a first electrode and a second electrode; a first transistor having a gate, a source and a drain, the gate of the first transistor being connected to one electrode of the photodiode; and a second transistor having a gate, a source and a drain, a read control circuit including a read control transistor having a source and a drain, one of the source and the drain of the read control transistor being connected to one of the source and the drain of the first transistor, and the other of the source and the drain of the read control transistor being connected to a first wiring which is configured to be supplied with a first reference potential, wherein the one of the source and the drain of the read control circuit is electrically connected to a second wiring which is configured to be supplied with a potential corresponding to intensity of light incident on the photodiode, wherein one of the source and the drain of the second transistor is electrically connected to the other of the source and the drain of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to a third wiring, wherein the third wiring is configured to be supplied with a second reference potential which is lower than the first reference potential, and wherein the read control transistor has a channel formation region comprising an oxide semiconductor. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification