Patent ID: 7566927

Claim:
A flash memory device, comprising: a memory cell array having a plurality of word lines, bit lines, string selection lines and cell strings, each cell string including a string selection transistor, a ground selection transistor and memory cells, all of which are connected to a corresponding bit line, each string selection line connected to corresponding string selection transistors; a bit line voltage setting circuit for setting a voltage on a bit line of a given memory cell to be programmed to a variable bit line voltage or a ground voltage; and a variable bit line voltage generating circuit for generating the variable bit line voltage, wherein the variable bit line voltage generating circuit increases the bit line voltage linearly proportional to the supply voltage if the supply voltage is lower than a given voltage level, and the variable bit line voltage generating circuit suppresses an increase if the supply voltage exceeds the given voltage level; wherein the given voltage level is lower than a difference value between a voltage of the string selection line and a threshold voltage of the string selection transistor.