Semiconductor memory device having self-correcting function

Abstract

A semiconductor memory device having a self-correcting function comprises memory cells for storing data and memory cells for storing parity bit data. The criterion of detecting in the first read circuit is set smaller and the criterion of detecting in the second read circuit is set greater in value than the current value read in such a state that the electric charge in the memory cell becomes depleted. In this way, the first read circuit detects a current value smaller and the second read circuit detects a current value greater than the value of the current flowing through the memory cell holding the bit error because of charge depletion. Consequently, even if the variation of the threshold resulting from the charge depletion allows the presence of a faulty memory cell, one of the read circuits can make a correct data read.