Claims
- 1. A nonvolatile memory device comprising:
a plurality of memory cells; and a first address counter circuit; wherein each of said memory cells has a source region, a drain region and a threshold voltage in either a first threshold voltage range or a second threshold voltage range, higher than said first threshold voltage range, the source regions of said memory cells are connected to each other and the drain regions of said memory cells are connected to each other, wherein said first address counter circuit generates an address signal adapted to select individual ones of said memory cells, and wherein when said nonvolatile memory is in a first operation, in which the threshold voltage of said memory cells is set at a value in said first threshold voltage range, each memory cell selected by said first address counter circuit is supplied a first voltage for changing the threshold voltage thereof from a value in said first threshold voltage range to a value in said second threshold voltage range, and then, said memory cells are supplied a different, second voltage for changing the threshold voltage of said memory cells from a value in said second threshold voltage range to a value in said first threshold voltage range.
- 2. A nonvolatile memory device according to claim 1, further comprising a verify circuit,
wherein after said plurality of memory cells are supplied said second voltage, said verify circuit verifies whether the threshold voltage attained by each of said memory cells selected by said first address counter circuit is in said first threshold voltage range or not.
- 3. A nonvoltage memory device according to claim 1, further comprising a second address counter circuit and a verify circuit,
wherein said second address counter circuit selects individual ones of said memory cells after said memory cells are supplied said second voltage, and wherein said verify circuit verifies whether the threshold voltage attained by each of said memory cells selected by said second address counter circuit is in said first threshold voltage range or not.
- 4. A nonvolatile memory device according to claim 3,
wherein said plurality of memory cells are supplied said second voltage again, when said verify circuit detects at least one memory cell with a threshold voltage that is not in said first threshold voltage range.
- 5. A nonvolatile memory device according to claim 4,
wherein said second address counter circuit holds an address when said verify circuit detects a threshold voltage of a memory cell of that address is not in said first threshold voltage range, and wherein said verify circuit verifies whether the threshold voltage attained by said memory cell of that address is in said first threshold voltage range or not, after said plurality of memory cells are supplied said second voltage.
- 6. A nonvolatile memory device according to claim 2,
wherein said verify circuit is capable of verifying said threshold voltage of ones of memory cells at once.
- 7. A nonvolatile memory device according to claim 5,
wherein said verify circuit is capable of verifying said threshold voltage of ones of memory cells at once.
Priority Claims (5)
Number |
Date |
Country |
Kind |
1-27271 |
Feb 1989 |
JP |
|
1-243603 |
Sep 1989 |
JP |
|
1-210262 |
Aug 1989 |
JP |
|
1-317477 |
Dec 1989 |
JP |
|
2-13614 |
Jan 1990 |
JP |
|
Parent Case Info
[0001] This application is a continuation of application Ser. No. 09/425,041, filed Oct. 19, 1999; which is a continuation of application Ser. No. 08/720,060, filed Sep. 27, 1996 (now U.S. Pat. No. 6,016,273); which was a continuation of application Ser. No. 08/456,797, filed Jun. 1, 1995 (now U.S. Pat. No. 5,781,476); which was a continuation of application Ser. No. 08/249,899, filed May 26, 1994 (now U.S. Pat. No. 5,844,842); and which, in turn, was (1) a continuation-in-part of application Ser. No. 08/144,500, filed Nov. 2, 1993 (now abandoned), which was a continuation of application Ser. No. 07/474,994, filed Feb. 5, 1990 (now abandoned), and was (2) a continuation-in-part of application Ser. No. 07/888,447, filed May 28, 1992 (now abandoned), which was a continuation of application Ser. No. 07/567,391, filed Aug. 14, 1990 (now abandoned); and the contents of all of which are incorporated herein by reference.
Continuations (7)
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Number |
Date |
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Parent |
09425041 |
Oct 1999 |
US |
Child |
09829053 |
Apr 2001 |
US |
Parent |
08720060 |
Sep 1996 |
US |
Child |
09425041 |
Oct 1999 |
US |
Parent |
08456797 |
Jun 1995 |
US |
Child |
08720060 |
Sep 1996 |
US |
Parent |
08249899 |
May 1994 |
US |
Child |
08456797 |
Jun 1995 |
US |
Parent |
07474994 |
Feb 1990 |
US |
Child |
08144500 |
Nov 1993 |
US |
Parent |
07888447 |
May 1992 |
US |
Child |
08144500 |
Nov 1993 |
US |
Parent |
07567391 |
Aug 1990 |
US |
Child |
07888447 |
May 1992 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
08144500 |
Nov 1993 |
US |
Child |
08249899 |
May 1994 |
US |