To provide a memory element where a desired potential can be stored as data without an increase in the number of power source potentials. The memory element stores data in a node which is brought into a floating state by turning off a transistor a channel of which is formed in an oxide semiconductor layer. The potential of a gate of the transistor can be increased by capacitive coupling between the gate and a source of the transistor. With the structure, a desired potential can be stored as data without an increase in the number of power source potentials.