A bit line load element for reducing a bit line amplitude during data reading is formed of p- and n-channel MOS transistors connected in parallel. When a word line is driven to the selected state, the p-channel MOS transistor is held off. In the data write operation, both the n- and p-channel MOS transistors are turned off. Even under a low power supply voltage, a sufficiently large bit line amplitude can be produced without an influence by a size of the bit line load element. By deactivating the bit line load element in the data write operation, it is possible to prevent generation of a DC current during data writing.