An object is to provide a semiconductor device that can maintain the connection relation between logic circuit units or the circuit configuration of each of the logic circuit units even after supply of power supply voltage is stopped. Another object is to provide a semiconductor device in which the connection relation between logic circuit units or the circuit configuration of each of the logic circuit units can be changed at high speed. In a reconfigurable circuit, an oxide semiconductor is used for a semiconductor element that stores data on the circuit configuration, connection relation, or the like. Specifically, the oxide semiconductor is used for a channel formation region of the semiconductor element.