Nonvolatile semiconductor memory device that erases stored data after a predetermined time period without the use of a timer circuit

摘要

A nonvolatile semiconductor memory device is characterized by including a memory cell to store data, a first reference cell, a check circuit to check a threshold of the first reference cell, and an erase circuit to erase the data of the memory cell in response to detection by the check circuit that the threshold of the first reference cell is smaller than or substantially equal to a predetermined fixed value.