ERASING NON-VOLATILE MEMORY SYSTEM HAVING ERROR CORRECTION CODE

PROBLEM TO BE SOLVED: To provide a method of erasing a non-volatile semiconductor memory device comprising determining the number of bit cells that failed to erase-verify during an erase operation among a subset of bit cells in a bit cell array including a plurality of bit cells.SOLUTION: The method comprises determining whether correction by means of an error correction code has been previously performed for the subset of bit cells. The erase operation is considered successful if the number of bit cells that failed to erase-verify after a predetermined number of erase pulses is below a threshold number and the correction by means of the error correction code has not been performed for the subset of bit cells.