A semiconductor device which can write and read multilevel data is provided. Anode connecting a source or a drain of an OS transistor and a gate of an OS transistor can hold the distribution of a plurality of potentials. A circuit configuration is employed in which the potential of the node is changed by capacitive coupling to control a conduction state of the OS transistor whose gate is connected thereto so that the potential of a gate of a Si transistor is changed. The potential of the gate of the Si transistor is changed positively in accordance with the potential change by capacitive coupling and is changed negatively in accordance with another transistor. In accordance with a change in value of current flowing through the Si transistor is detected, written data is read.