Patent ID: 7221616

Claim:
A word line driver circuit for applying a boost voltage to a word line, wherein the boost voltage is used for operating an access transistor of a memory cell in a semiconductor memory device, the word line driver circuit comprising: an input node, which has a ground voltage level during a non-selected operating mode and to which an output signal of a word line decoding circuit is applied with a power source voltage level during a selected operating mode; an output node, which has a ground voltage level during the non-selected operating mode, and which applies a voltage having a level higher than a level of the power source voltage to a word line connected to the memory cell during the selected operating mode; a capacitor, of which one electrode is connected to the output node and which boosts the output node to a voltage having a level higher than a level of the power source voltage during the selected operating mode; a first transistor connected between the input node and the output node and controlled by a first control signal that has a level of the power source voltage during the selected operating mode, wherein the first transistor is for floating the output node during the selected operating mode; a second transistor connected between the input node and a control node and operating by the power source voltage, wherein the second transistor is for floating the control node during the selected operating mode; and a third transistor connected between a node to which a second control signal that has a level of the power source voltage during the selected operating mode is applied, and another electrode of the capacitor, and controlled by a voltage of the control node, wherein the third transistor is for transferring the second control signal that has a level of the power source voltage to the capacitor during the selected operating mode, whereby the voltage at the output node is substantially equal to two times the power source voltage less a threshold voltage of the second transistor.