FLASH MEMORY DEVICE HAVING UNIFORM THRESHOLD VOLTAGE DISTRIBUTION WITHOUT UNDER-PROGRAMMED CELLS AND OVER-PROGRAMMED CELLS AND METHOD FOR VERIFYING THE SAME

摘要

PURPOSE: A flash memory device having a uniform threshold voltage distribution without under-programmed cells and over-programmed cells and a method for verifying an under-program and an over-program are provided to improve the uniformity of a threshold voltage distribution by maintaining a program verification voltage in a constant level during the predetermined number of program cycle. CONSTITUTION: A memory cell array block(110) is provided with a plurality of flash memory cells. A program verification voltage generator(410) generates a program verification voltage for confirming whether the flash memory cells are programmed or not. A word line level selector(130) transmits the program verification voltage to a word line connected to control gates of the flash memory cells. A page buffer(420) includes a latch for storing data of the flash memory cells to reset the latch whenever the program verification voltage becomes a low level.