A semiconductor device includes a DRAM cell configured to store a data; and a sense amplifier activated in response to supply of power supply voltages and configured to sense the data stored in the DRAM cell. A power supply circuit supplies the power supply voltages to the sense amplifier. A sense amplifier dummy circuit provides a replica of a state of the sense amplifier immediately after the activation of the sense amplifier; and a power supply control circuit controls the power supply circuit based on the replica such that the power supply voltages are varied with time.