SEMICONDUCTOR MEMORY DEVICE

摘要

PURPOSE:To shorten the time for verifying the erasure of a flash memory. CONSTITUTION:A dummy cell DC showing a similar characteristic of the erasing distribution to that of an a nonvolatile memory cell MC is provided corresponding to at least one column or one row of a memory array 1. The dummy cell DC is erased at one time together with the nonvolatile memory cell MC. Data of the dummy cell DC is read out instead of reading the nonvolatile memory cell MC to confirm the erasure. Accordingly, by confirming the read data of the dummy cell DC, the number of bites to carry out the verification is reduced and the time necessary for the verification of the erasure is shortened.