| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To freely change a threshold distribution according to the reliability of a memory cell. <P>SOLUTION: Memory cells in a memory can be divided into 1st and 2nd memory cell groups. To the 1st memory cell group, writing is carried out in the 1st mode so that 1st threshold distribution can be obtained. To the 2nd memory cell group, writing is carried out in the 2nd mode so that 2nd threshold distribution different from the 1st threshold distribution can be obtained. Changeover between the 1st mode and the 2nd mode is controlled by a threshold distribution control circuit. A different threshold distribution can be realized by, for example, controlling a step-up width of a write potential. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
