In a method for supplying power supply voltages in a semiconductor memory device a first source voltage is applied to a memory cell of a memory cell array as a cell array internal voltage for operating a sense amplifier coupled to the memory cell. A second source voltage is applied as a word line drive voltage of the memory cell array. The second source voltage has a voltage level higher than a voltage level of the first source voltage. The second source voltage is also applied as a drive voltage of an input/output line driver to drive write data into an input/output line in a write operating mode.