The present invention provides a thin semiconductor device in which its security such as prevention of counterfeit or information leakage is to be enhanced. One feature of the present invention is a thin semiconductor device in which a plurality of thin film integrated circuits are mounted and in which at least one integrated circuit is different from the other integrated circuits in any one of a specification, layout, frequency for transmission or reception, a memory, a communication means, a communication rule and the like. According to the present invention, a thin semiconductor device tag having the plurality of thin film integrated circuits communicates with a reader/writer and at least one of the thin film integrated circuits receives a signal to write information in a memory, and the information written in the memory determines which of the thin film integrated circuits communicates.