| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the unnecessary verifying by setting the word line voltage according to the distribution state of threshold voltage in a verification mode, deciding a latching circuit according to whether or not the threshold of a memory cell exceeds the voltage applied to the word line and skipping the verifying of a prescribed distribution according to the writing state in a verifying operation mode. SOLUTION: The output of a counter 1 is supplied to comparators 3 and 4, and the ISPP of a word line voltage control circuit is driven. The write frequency at which the satisfactory writing is decided for a cell of the highest writing speed, based on the higher order distribution data is set to the comparator 3. The comparator 3 sets an output CMP1 at low level, when the writing frequency exceeds its set level. The comparator 4 sets an output CMP2 at high level, when the writing frequency exceeds its set level at which the satisfactory writing is decided for a cell of the lowest writing speed, based on the lower order distribution data.</p> |
