NONVOLATILE SEMICONDUCTOR MEMORY DEVICE

摘要

PROBLEM TO BE SOLVED: To improve charge holding characteristics.SOLUTION: A nonvolatile semiconductor memory device comprises: a memory cell array 5 including a plurality of memory cell transistors MTr each storing information depending on a threshold level of n value (n is an integer of greater than 2); and a control circuit 10 controlling the memory cell array. In write operation, the control circuit shifts the threshold level of the plurality of memory cell transistors to a base threshold level that is a threshold level other than a threshold level of the highest voltage and a threshold level of the lowest voltage among the threshold level of n value, and then shifts the threshold level of the plurality of memory cell transistors to any one of the threshold levels of n value.