NON-VOLATILE SEMICONDUCTOR MEMORY AND DATA ERASING METHOD FOR NON-VOLATILE SEMICONDUCTOR MEMORY

摘要

PROBLEM TO BE SOLVED: To provide a flash memory in which an erasing time is shortened. SOLUTION: In a flow in which erasure is performed two times to narrow the distribution width of threshold voltage of a memory cell and to reduce the number of memory transistors being object of over-erase-verify. Erasure verify-voltage for the first time erasure (S41, S42) is made higher than that for the second time erasure (S44, S46). The number of erasure pulses at the second time erasure can be reduced, and an erasure time can be shortened further.