Data writing method for semiconductor memory device and semiconductor memory device

• US 6,870,773 B2
• Filed: 03/10/2004
• Issued: 03/22/2005
• Est. Priority Date: 02/20/2001
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Goda, Akira, Noguchi, Mitsuhiro, Takeuchi, Yuji
• Primary Examiner(s): Elms, Richard
• Assistant Examiner(s): Nguyen, Tuan T.
• Application Number:
  US10/796,180
• Publication Number:
  US 20040179403A1
• Time in Patent Office: 377 Days
• Field of Search: 365/185.22, 365/185.28
• US Class Current: 365/185.22
• CPC Class Codes: G11C 16/0416 comprising cells containing a single floating gate transistor and no select transistor, e.g. UV EPROM
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/12 Programming voltage switching circuits
• CPC Class Codes: G11C 16/3445 Circuits or methods to verify correct erasure of nonvolatile memory cells
• CPC Class Codes: G11C 16/3468 Prevention of overerasure or overprogramming, e.g. by verifying whilst erasing or writing

Abstract

A semiconductor memory device includes a first memory cell block capable of rewriting data and having at least one first memory cell, and a second memory cell block capable of rewriting data and having at least one second memory cell adjoining the first memory cell. A data writing method for the semiconductor memory device includes writing data into the first memory cell, writing data into the second memory cell following writing the data into the first memory cell, verifying the data of the first memory cell after writing the data into the second memory cell, and rewriting the data into the first memory cell when insufficiency of the data of the first memory cell as a result of verifying the data of the first memory cell.

Claims

1. A data writing method for a semiconductor memory device having a first memory cell block capable of rewriting data and having at least one first memory cell;

and a second memory cell block capable of rewriting data and having at least one second memory cell adjoining said first memory cell, said method comprising;

writing data into said first memory cell;

writing data into said second memory cell following writing the data into said first memory cell;

verifying the data of said first memory cell after writing the data into said second memory cell; and

rewriting the data into said first memory cell when insufficiency of the data of said first memory cell as a result of verifying the data of said first memory cell.

2. The method according to claim 1, wherein said first and second memory cells have an charge accumulation layer, respectively, in which the electric charge is injected or discharged in association with the data to be stored and store the data of 2 values or more as an electric charge amount.

3. The method according to claim 1, wherein said first and second memory cells have an charge accumulation layer, respectively, in which the electric charge is injected or discharged in association with the data to be stored, store the data of 2 values or more as an electric charge amount and store the data of 3 values or more supplied from the outside in association with the data of 2 values of each of said first and second memory cells.

4. The method according to claim 1, wherein each of said first and second memory cells comprises an field effect transistor having at least one charge accumulation layer and at least one control gate.

5. The method according to claim 4, wherein said field effect transistors are formed on the same conductive type well, respectively.

6. The method according to claim 4, wherein said field effect transistors use an FN tunneling current for the writing operation.

7. The method according to claim 4, wherein each of said first and second memory cells includes at least first and second cell transistors adjoining each other, each of said first and second cell transistor have a source electrode, a drain electrode and said charge accumulation layer, said source electrode of said first cell transistor and said drain electrode of said second cell transistor are connected in series with each other, and a distance between said charge accumulation layer of said first cell transistor and said charge accumulation layer of said second cell transistor is less than twice a thickness of said charge accumulation layer.

8. The method according to claim 7, wherein an insulator is formed between the charge accumulation layer of said first memory cell and the charge accumulation layer of said second memory cell.

9. The method according to claim 4, wherein said charge accumulation layer comprises an insulator.

10. A data writing method for a semiconductor memory device having a memory cell block capable of rewriting data, wherein said memory cell block has at least two first and second memory cells connected in series or in parallel and adjoin each other, said method comprising:

writing data into said first memory cell;

writing data into said second memory cell following writing the data into said first memory cell;

verifying the data of said first memory cell after writing the data into said second memory cell; and

rewriting the data into said first memory cell when insufficiency of the data of said first memory cell as a result of verifying the data of said first memory cell.

11. The method according to claim 10, wherein said first and second memory cells have an charge accumulation layer, respectively, in which the electric charge is injected or discharged in association with the data to be stored and store the data of 2 values or more as an electric charge amount.

12. The method according to claim 10, wherein said first and second memory cells have an charge accumulation layer, respectively, in which the electric charge is injected or discharged in association with the data to be stored, store the data of 2 values or more as an electric charge amount and store the data of 3 values or more supplied from the outside in association with the data of 2 values of each of said first and second memory cells.

13. The method according to claim 10, wherein each of said first and second memory cells comprises an field effect transistor having at least one charge accumulation layer and at least one control gate.

14. The method according to claim 13, wherein said field effect transistors are formed on the same conductive type well, respectively.

15. The method according to claim 13, wherein said field effect transistors use an FN tunneling current for the writing operation.

16. The method according to claim 13, wherein each of said first and second memory cells includes at least first and second cell transistors adjoining each other, each of said first and second cell transistor have a source electrode, a drain electrode and said charge accumulation layer, said source electrode of said first cell transistor and said drain electrode of said second cell transistor are connected in series with each other, and distance between said charge accumulation layer of said first cell transistor and said charge accumulation layer of said second cell transistor is less than twice a thickness of said charge accumulation layer.

17. The method according to claim 16, wherein an insulator is formed between the charge accumulation layer of said first memory cell and the charge accumulation layer of said second memory cell.

18. The method according to claim 13, wherein said charge accumulation layer comprises an insulator.