| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent an undesirable current from flowing into an unselected nonvolatile memory cell. <P>SOLUTION: Each of a plurality of nonvolatile memory cells (MC) can store data in accordance with level of a threshold voltage, and the low threshold voltage level is regarded as a negative voltage area, and the high threshold voltage level is regarded as a positive voltage area. Respective operation controls for a 1st operation that the nonvolatile memory cell of low threshold voltage level is changed to be the high threshold voltage level and for a 2nd operation that the nonvolatile memory cell of high threshold voltage level is changed to be the low threshold voltage level, are carried out for the nonvolatile memory. When the 1st operation is for a write-in operation and the 2nd operation is for an erasing operation, the threshold voltage is lowered after the light writing operation is carried out beforehand from a viewpoint of voltage or voltage applying time in the erasing operation. When the threshold voltage is made to be low, such a state that the threshold voltage of 1-element/1-cell type memory cell made into a depletion type is transferred to an undesirable low level can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
