| 摘要 |
<p>PURPOSE: To prevent over erasing by preforming adequate erasing operation for memory cells other then memory cells (defective cells) in which erasing is slow. CONSTITUTION: When 'erasing to/from erasing verifying' is repeated in erasing operation of a memory cell array (7), a defective count circuit (10) is operated. When it is judged that the number of cells in which erasing are not yet finished (cells in which erasing is slow) are less than the prescribed numbers, by finishing erasing operation, adequate erasing operation for almost cells excluding cells of several bits in which erasing is slow can be realized, and over erasing is prevented.</p> |
