| 摘要 |
A method for operating a semiconductor flash memory device is provided to reduce a threshold voltage range of MOS transistors of a unit cell after programmed. According to a method for operating a semiconductor flash memory device, a first programming voltage is applied to a number of unit cells to be programmed. A first verify pulse(V1) is applied to the unit cells to verify programming state. A second verify pulse(V2) with a higher voltage level than the first verify pulse is applied to a unit cell determined not to be programmed by the first verify pulse. A second program voltage is applied to the unit cell judged to be programmed by the second verify pulse, not by the first verify pulse. The second program voltage is obtained by adding a first step voltage and the first programming voltage. A third programming voltage is applied to the unit cell not programmed by the first and the second verify pulse. The third programming voltage is obtained by adding the first programming voltage and a second step voltage. |
