A semiconductor device having excellent data retention characteristics. A transistor with a low off-state current is utilized to save and retain data stored in a memory circuit, and a potential to be applied to a back gate of the transistor is applied from a battery provided for each memory circuit. The potential applied to the back gate of the transistor and a potential for charging the battery are generated in a voltage generation circuit. The battery is charged utilizing power gating of the memory circuit and data retention characteristics is improved.