| 摘要 |
<p>PURPOSE:To prevent an over-erasure cell from being generated by controlling threshold values of memory cell transistors at the time of erasing a nonvolatile semiconductor memory capable of being electrically erased. CONSTITUTION:This device has a positive potential impressing circuit 13 making potentials of control gates higher than a grounding potential. Then, the over- erasure cell 27 is prevented from being generated by controlling the distribution of threshold voltages of memory cells at the time of an erasing to a direction in which the threshold value is high.</p> |
