A semiconductor memory device includes a sub-wordline and a bit line connected to a memory cell, a sub-wordline driver for signaling the sub-wordline, and a main word decoder and a sub-word decoder, for selecting the sub-wordline driver in response to an external input address signal, wherein the wordline driver includes an NMOS transistor switch connected between a main wordline which is an output of the main word decoder and the sub-wordline, and wherein the logic "high" voltage level of a first control signal which controls the switch is lower than that of a signal output to the sub-wordline. The semiconductor memory device having the sub-wordline driver allows the internal power supply voltage to be used as the power supply voltage of the main word decoder. Accordingly, the reliability of a gate oxide film of a transistor constituting the main word decoder is improved, which lengthens the life of the semiconductor memory device.