A semiconductor device including a pair of stacked semiconductor ICs capable of communicating with each other by wireless. Each IC has: a transmitter circuit operable to send, by wireless, transmit data together with a clock signal deciding a transmission timing, and arranged so that the wireless transmission timing is adjustable; a receiver circuit operable to receive data in synchronization with a clock signal received by wireless, and arranged so that its wireless reception timing is adjustable; and a control circuit operable to perform timing adjustments of the transmitter and receiver circuits based on a result of authentication of data returned by the other IC in response to data transmitted through the transmitter circuit, and received by the receiver circuit. This arrangement for near field communication between stacked semiconductor ICs enables: reduction of the scale of a circuit for communication timing adjustment; and highly accurate adjustment of the communication timing.