| CPC G11C 16/10 (2013.01) [G11C 11/5628 (2013.01); G11C 16/0483 (2013.01); G11C 16/08 (2013.01); G11C 16/26 (2013.01); G11C 16/34 (2013.01); G11C 16/3427 (2013.01); G11C 16/3459 (2013.01); G11C 11/5642 (2013.01); G11C 2211/5641 (2013.01)] | 20 Claims |

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1. A memory system comprising:
a semiconductor memory device including a plurality of memory cells and a word line, the plurality of memory cells corresponding to a first page, the plurality of memory cells comprising first, second, third, and fourth memory cells, the word line being electrically connected to gates of the first, second, third, and fourth memory cells; and
a controller configured to issue a first write command and a second write command to the semiconductor memory device, wherein
the semiconductor memory device is configured to:
execute, in response to the issued first write command, a first program operation on the first page and a first verify operation on the first page using a first verify condition, and
execute, in response to the issued second write command,
a second program operation selectively on a first subset of the first page, the first subset corresponding to the first and second memory cells and not to the third and fourth memory cells, and a second verify operation selectively on the first subset of the first page using a second verify condition when the second write command corresponds to the first subset of the first page, and
the second program operation selectively on a second subset of the first page, the second subset corresponding to the third and fourth memory cells and not to the first and second memory cells, and a third verify operation selectively on the second subset of the first page using a third verify condition when the second write command corresponds to the second subset of the first page.
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