Patent ID: 7539057

Claim:
A program method of a flash memory device including a plurality of memory cells that share word lines and bit lines, the program method comprising the steps of: selecting one of the word lines; programming memory cells connected to the selected word line, of the plurality of memory cells, by applying a start program voltage to the selected word line; selecting memory cells respectively having threshold voltages lower than a predetermined voltage based on a first verify voltage, of the memory cells connected to the selected word line; programming the selected memory cells by applying a pre-program voltage to the selected word line after applying the start program voltage, wherein the pre-program voltage is higher than the start program voltage; prohibiting programming into the remaining memory cells other than the selected memory cells when the selected memory cells are programmed; and additionally programming the memory cells connected to the selected word line, while supplying a program voltage that gradually rises from the start program voltage at the ratio of a step voltage to the selected word line, the additionally programming being verified with a second verify voltage, wherein the second verify voltage is higher than the first verify voltage.