NONVOLATILE SEMICONDUCTOR MEMORY AND COMPUTER SYSTEM EMPLOYING IT

摘要

PROBLEM TO BE SOLVED: To obtain a nonvolatile semiconductor memory having enhanced rewrite resistance and a computer system employing it. SOLUTION: Rewriting operation continues only for such memory cell as the threshold voltage has not yet reached the verify word line voltage after finishing the rewriting (write, erase) operation. Since the threshold voltage of memory cell can be matched on the writing side and erasing side, total quantity of charges to be passed through an insulation film can be reduced at the time of rewriting operation and the rewriting resistance can be enhanced.