A semiconductor memory device is provided with a plurality of sense amplifiers adapted and configured to sense and amplify data stored in memory cells, a sense amplifier control unit adapted and configured to generate a driving voltage for driving the plurality of sense amplifiers, and a identification unit adapted and configured to generate an bit organization identification signal which represents a I/O structure and output the signal to the sense amplifier control unit. Here, the sense amplifier control unit regulates a level of the driving voltage in response to the bit organization identification signal. The semiconductor memory device supplies an optimized power source in each mode, thereby reducing current consumption and improving operating characteristics.