| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve reliability of a non-volatile semiconductor ensuring operation margin by narrowing distribution width of a threshold voltage (Vtm) of a memory cell after erasure, also by preventing the occurrence of over-erasure. SOLUTION: This memory is provided with reference cells 113, 114, having cell structure being equivalent to a memory cell 106 of a main body side. When batch erasure is conducted on an erasure block of a memory cell array 107, voltage dropped from erasure voltage of the memory cell of the body side by a prescribed value and voltage raised by the prescribed values are applied respectively. Control is performed, so that threshold of the reference cells 113, 114 are in the prescribed range after the erasure. Thereby, verification is not required for all memory cells, and also the occurrence of over-erasure can be prevented.</p> |
