SEMICONDUCTOR DEVICE AND DRIVING METHOD THEREOF

• US 20110215861A1
• Filed: 03/01/2011
• Published: 09/08/2011
• Est. Priority Date: 03/08/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: IKEDA, Takayuki, KUROKAWA, Yoshiyuki, AOKI, Takeshi, KOZUMA, Munehiro
• Granted Patent: US 8,976,155 B2
• Time in Patent Office: Days
• US Class Current: 327/537
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array

Abstract

A semiconductor device includes a photodiode, a first transistor, a second transistor, and a third transistor. The second transistor and the third transistor have a function of retaining a charge accumulated in a gate of the first transistor. In a period during which the second transistor and the third transistor are off, a voltage level of a voltage applied to a gate of the second transistor is set to be lower than a voltage level of a source of the second transistor and a voltage level of a drain of the second transistor, and a voltage level of a voltage applied to a gate of the third transistor is set to be lower than a voltage level of a source of the third transistor and a voltage level of a drain of the third transistor.

Claims

1. A semiconductor device comprising:

a photodiode;

a first transistor;

a second transistor;

a third transistor; and

a fourth transistor,

wherein a first terminal of the photodiode is electrically connected to a first terminal of the second transistor,

wherein a second terminal of the second transistor is electrically connected to a gate of the first transistor and a first terminal of the third transistor,

wherein a first terminal of the first transistor is electrically connected to a first terminal of the fourth transistor,

wherein in a first period, a charge corresponding to an amount of incident light to the photodiode is accumulated to the gate of the first transistor,

wherein in a second period, the charge is retained in the gate of the first transistor while a first voltage is supplied to a gate of the second transistor and a second voltage is supplied to a gate of the third transistor, and

wherein a voltage level of the first voltage is lower than a voltage level of the first terminal of the second transistor and a voltage level of the second terminal of the second transistor, and a voltage level of the second voltage is lower than a voltage level of the first terminal of the third transistor and a voltage level of a second terminal of the third transistor.

2. The semiconductor device according to claim 1,

wherein a semiconductor layer of the second transistor comprises an oxide semiconductor.

3. The semiconductor device according to claim 1,

wherein a semiconductor layer of the third transistor comprises an oxide semiconductor.

4. The semiconductor device according to claim 1,

wherein a semiconductor layer of the second transistor and a semiconductor layer of the third transistor comprise an oxide semiconductor.

5. The semiconductor device according to claim 1,

wherein the voltage level of the first voltage is lower than a voltage level of a second terminal of the photodiode.

6. The semiconductor device according to claim 1,

wherein the charge is discharged from the gate of the first transistor while a third voltage is supplied to the gate of the third transistor and a fourth voltage is supplied to the second terminal of the third transistor.

7. The semiconductor device according to claim 1,

wherein the charge is discharged from the gate of the first transistor while a fifth voltage is supplied to a second terminal of the photodiode and a sixth voltage is supplied to the gate of the second transistor.

8. A semiconductor device comprising:

a photodiode;

a first transistor;

a second transistor; and

a third transistor,

wherein a first terminal of the photodiode is electrically connected to a first terminal of the second transistor,

wherein a second terminal of the second transistor is electrically connected to a gate of the first transistor and a first terminal of the third transistor,

wherein in a first period, a charge corresponding to an amount of incident light to the photodiode is accumulated to the gate of the first transistor,

wherein in a second period, the charge is retained in the gate of the first transistor while a first voltage is supplied to a gate of the second transistor and a second voltage is supplied to a gate of the third transistor, and

wherein a voltage level of the first voltage is lower than a voltage level of the first terminal of the second transistor and a voltage level of the second terminal of the second transistor, and a voltage level of the second voltage is lower than a voltage level of the first terminal of the third transistor and a voltage level of a second terminal of the third transistor.

9. The semiconductor device according to claim 8,

wherein a semiconductor layer of the second transistor comprises an oxide semiconductor.

10. The semiconductor device according to claim 8,

wherein a semiconductor layer of the third transistor comprises an oxide semiconductor.

11. The semiconductor device according to claim 8,

wherein a semiconductor layer of the second transistor and a semiconductor layer of the third transistor comprise an oxide semiconductor.

12. The semiconductor device according to claim 8,

wherein the voltage level of the first voltage is lower than a voltage level of a second terminal of the photodiode.

13. The semiconductor device according to claim 8,

wherein the charge is discharged from the gate of the first transistor while a third voltage is supplied to the gate of the third transistor and a fourth voltage is supplied to the second terminal of the third transistor.

14. The semiconductor device according to claim 8,

wherein the charge is discharged from the gate of the first transistor while a fifth voltage is supplied to a second terminal of the photodiode and a sixth voltage is supplied to the gate of the second transistor.

15. A semiconductor device comprising:

a photodiode;

a first transistor; and

a second transistor;

wherein a first terminal of the photodiode is electrically connected to a first terminal of the second transistor,

wherein a second terminal of the second transistor is electrically connected to a gate of the first transistor,

wherein in a first period, a charge corresponding to an amount of incident light to the photodiode is accumulated to the gate of the first transistor,

wherein in a second period, the charge is retained in the gate of the first transistor while a first voltage is supplied to a gate of the second transistor, and

wherein a voltage level of the first voltage is lower than a voltage level of the first terminal of the second transistor and a voltage level of the second terminal of the second transistor.

16. The semiconductor device according to claim 15,

wherein a semiconductor layer of the second transistor comprises an oxide semiconductor.

17. The semiconductor device according to claim 15,

wherein the voltage level of the first voltage is lower than a voltage level of a second terminal of the photodiode.

18. The semiconductor device according to claim 15,

wherein the charge is discharged from the gate of the first transistor while a fifth voltage is supplied to a second terminal of the photodiode and a sixth voltage is supplied to the gate of the second transistor.

19. A driving method of a semiconductor device comprising:

accumulating a charge to a gate of a first transistor by supplying a first voltage to a first terminal of a photodiode, a second voltage to a gate of a second transistor, and a third voltage to a gate of a third transistor,

retaining the charge in the gate of the first transistor by supplying a fourth voltage to the gate of the second transistor and a fifth voltage to the gate of the third transistor, and

discharging the charge from the gate of the first transistor by supplying a sixth voltage to the gate of the third transistor and a seventh voltage to a first terminal of the third transistor,

wherein the charge corresponds to an amount of incident light to the photodiode, and

wherein a voltage level of the fourth voltage is lower than a voltage level of a first terminal of the second transistor and a voltage level of a second terminal of the second transistor, and a voltage level of the fifth voltage is lower than a voltage level of the first terminal of the third transistor and a voltage level of a second terminal of the third transistor in retaining.

20. The driving method according to claim 19,

wherein a voltage level of the third voltage equals to the voltage level of the fifth voltage.

21. A driving method of a semiconductor device comprising:

accumulating a charge to a gate of a first transistor by supplying a first voltage to a first terminal of a photodiode, and a second voltage to a gate of a second transistor,

retaining the charge in the gate of the first transistor by supplying a third voltage to the gate of the second transistor, and

discharging the charge from the gate of the first transistor by supplying a fourth voltage to the gate of the second transistor and a fifth voltage to the first terminal of the photodiode,

wherein the charge corresponds to an amount of incident light to the photodiode, and

wherein a voltage level of the third voltage is lower than a voltage level of a first terminal of the second transistor and a voltage level of a second terminal of the second transistor in retaining.

22. The driving method according to claim 21,

wherein a voltage level of the second voltage equals to a voltage level of the fourth voltage.