A semiconductor device with improved reliability, in which increase in power consumption can be reduced. The semiconductor device includes an antenna for transmitting and receiving a wireless signal to/from a communication device and at least first and second functional circuits electrically connected to the antenna. The first functional circuit includes a power supply control circuit for controlling power supply voltage output from a power supply circuit in the second functional circuit. A power supply control circuit in the second functional circuit includes a transistor of which first terminal is electrically connected to an output terminal of the power supply circuit and second terminal is electrically connected to a ground line. A gate terminal of the transistor is electrically connected to the power supply control circuit included in one functional circuit.