A semiconductor device that enables lower power consumption and data storage imitating a human brain is provided. The semiconductor device includes a control unit, a memory unit, and a sensor unit. The memory unit includes a memory circuit and a switching circuit. The memory circuit includes a first transistor and a capacitor. The switching circuit includes a second transistor and a third transistor. The first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and a back gate electrode. The control unit has a function of switching a signal supplied to the back gate electrode, in accordance with a signal obtained at the sensor unit.