| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a semiconductor storage device capable of reading stored data without fail even if a margin between threshold voltage distributions is narrow. <P>SOLUTION: In a semiconductor storage device, a control part sets a threshold voltage of a memory cell to a first level by an erase operation, sets the threshold voltage of the memory cell to a first level, a second level,..., the n-th level (n=2<SP POS="POST">k</SP>) in accordance with a write data inputted from outside by repeating write and verify operations to store k-bit data, counts a number of write operations of j times (j is a natural number) in a cell exceeding the (h-1)-th level among cells written to the h-th level (h≤n) after exceeding the (h-1)-th level, and slows down a writing speed on and after the j-th write operations. <P>COPYRIGHT: (C)2012,JPO&INPIT |
