Patent ID: 7379342
Filing Date: 2008-05-27
Classification: G11C

Abstract:
1. Method of programming a flash memory device, comprising the steps of: (a) performing a first program operation so that each threshold voltage of flash memory cells becomes higher than a target threshold voltage; (b) establishing a comparative voltage higher than the target threshold voltage; (c) performing a first program verification operation by which each threshold voltage of the memory cells is compared to the comparative voltage to verify whether the memory cells are programmed; (d) if flash memory cells have a threshold voltage lower than the comparative voltage, performing a second program operation so that the detected flash memory cells have a threshold voltage higher than the comparative voltage; (e) performing a second program verification operation for determining whether each threshold voltage of the memory cells is higher than the comparative voltage by comparing the comparative voltage with each threshold voltage of the memory cells; (f) lowering the comparative voltage; and (g) repeating the steps of (d) and (e) so that all of the flash memory cells have a threshold voltage higher than the comparative voltage.