Patent ID: 7061803

Claim:
A method for preserving a word line pass bias in a NAND-type flash memory, comprising the steps of: generating a program precharge signal and a program precharge delay signal delayed from the program precharge signal in a ROM block formed in a peripheral circuit coupled to a memory cell array of the NAND-type flash memory; synchronizing the program precharge signal and the program precharge delay signal with a program precharge signal for a block word line transmitted to the block word line and a program precharge signal for group access transmitted to a group access signal generation circuit, and separating the signals; turning on/off a precharge switch in a precharge circuit coupled to the block word line according to the program precharge signal for group access; precharging a high voltage to the block word line when the precharge switch is turned on; turning on at least one of pass switches coupled to the block word line according to a block select address signal, for programming a cell coupled to the pass switch; turning on a discharge switch according to the program precharge signal for the block word line or the block select address signal; and when the discharge switch is turned on, discharging the high voltage precharged to the block word line.