Semiconductor memory device having a reading transistor with a back-gate electrode

• US 8,588,000 B2
• Filed: 05/16/2011
• Issued: 11/19/2013
• Est. Priority Date: 05/20/2010
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kamata, Koichiro
• Primary Examiner(s): Tran, Andrew Q
• Application Number:
  US13/108,636
• Publication Number:
  US 20110286256A1
• Time in Patent Office: 918 Days
• Field of Search: 365/185.23, 365/185.27, 365/185.03, 365/185.08, 365/185.1
• US Class Current: 365/185.1
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: G11C 11/565 using capacitive charge storage elements
• CPC Class Codes: G11C 16/24 Bit-line control circuits
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H10B 41/30 characterised by the memory core region

Abstract

A semiconductor device with a reduced area and capable of higher integration and larger storage capacity is provided. A multi-valued memory cell including a reading transistor which includes a back gate electrode and a writing transistor is used. Data is written by turning on the writing transistor so that a potential according to the data is supplied to a node where one of a source electrode and a drain electrode of the writing transistor and a gate electrode of the reading transistor are electrically connected to each other, and then turning off the writing transistor and holding a predetermined potential in the node. Data is read by supplying a reading control potential to a control signal line connected to one of a source electrode and a drain electrode of the reading transistor, and then detecting potential change of a reading signal line.

Claims

1. A semiconductor device comprising:

a memory cell which comprises a first transistor and a second transistor;

a first wiring;

a second wiring;

a third wiring; and

a fourth wiring,

wherein one of a source electrode and a drain electrode of the first transistor is electrically connected to the first wiring,

wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to the fourth wiring,

wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to a gate electrode of the first transistor,

wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to the second wiring,

wherein a gate electrode of the second transistor is electrically connected to the third wiring, and

wherein the first transistor comprises a back gate electrode.

2. The semiconductor device according to claim 1,

wherein the memory cell further comprises a capacitor, and

wherein the capacitor is electrically connected to the gate electrode of the first transistor.

3. The semiconductor device according to claim 1, wherein the back gate electrode is electrically connected to the first wiring.

4. The semiconductor device according to claim 1, wherein the second transistor comprises an oxide semiconductor.

5. The semiconductor device according to claim 1, wherein the first transistor comprises an oxide semiconductor.

6. An electronic device comprising the semiconductor device according to claim 1.

7. A semiconductor device comprising:

a memory cell which comprises a first transistor and a second transistor;

a first wiring;

a second wiring;

a third wiring; and

a fourth wiring,

wherein one of a source electrode and a drain electrode of the first transistor is electrically connected to the first wiring,

wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to the fourth wiring,

wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to a gate electrode of the first transistor,

wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to the second wiring,

wherein a gate electrode of the second transistor is electrically connected to the third wiring,

wherein the first transistor comprises a back gate electrode, and

wherein at least one of the first transistor and the second transistor comprises an oxide semiconductor and the oxide semiconductor comprises In, Ga, and Zn.

8. The semiconductor device according to claim 7,

wherein the memory cell further comprises a capacitor, and

wherein the capacitor is electrically connected to the gate electrode of the first transistor.

9. The semiconductor device according to claim 7, wherein the back gate electrode is electrically connected to the first wiring.

10. An electronic device comprising the semiconductor device according to claim 7.

11. A semiconductor device comprising:

a memory cell which comprises a first transistor and a second transistor;

a first wiring;

a second wiring;

a third wiring; and

a fourth wiring,

wherein one of a source electrode and a drain electrode of the first transistor is electrically connected to the first wiring,

wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to the fourth wiring,

wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to a gate electrode of the first transistor,

wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to the second wiring,

wherein a gate electrode of the second transistor is electrically connected to the third wiring,

wherein the first transistor comprises a back gate electrode, and

wherein at least one of the first transistor and the second transistor comprises an oxide semiconductor.

12. The semiconductor device according to claim 11,

wherein the memory cell further comprises a capacitor, and

wherein the capacitor is electrically connected to the gate electrode of the first transistor.

13. The semiconductor device according to claim 11, wherein the back gate electrode is electrically connected to the first wiring.

14. An electronic device comprising the semiconductor device according to claim 11.