| 摘要 |
<P>PROBLEM TO BE SOLVED: To shorten the time needed for program verification and erasure verification and also to prevent the threshold voltage from changing too much even if rewriting and reerasing are performed. <P>SOLUTION: This nonvolatile semiconductor storage device is provided with a plurality of electrically rewritable nonvolatile semiconductor memory cells, a word line connected to the plurality of memory cells in common, a source line connected to the plurality of memory cells in common, a row decoder for supplying the word line with write verification voltage, a plurality of bit lines connected to the corresponding bit lines respectively, and a plurality of write verifying circuits provided in the corresponding bit lines respectively. Each of the write verifying circuit stores data of a first or second logical level. The write verifying circuits charge a corresponding bit line in advance and detect a write state of the corresponding memory cells after a prescribed time in the case of storing the data of the first logical level. The write verifying circuits connect a corresponding bit line to a prescribed power supply at least for the prescribed time in the case of storing the data of the second logical level. <P>COPYRIGHT: (C)2004,JPO |
