An object of the present invention is to reduce, during the standby time, the electric power caused by the leakage current flowing through a storage transistor in a 3-transistor dynamic cell. The present invention is configured as follows. Source electrodes of storage transistors in a plurality of 3-transistor dynamic cells constituting a memory array are connected, and a switch is provided between the source electrode and a power supply terminal. The leakage current during the standby time is interrupted by bringing the switch into a conducting state during the active time, and by bringing the switch into a nonconducting state during the standby time.