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 aspecification, 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 taghaving 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.