Application form of and demand for an IC chip formed with a silicon wafer are expected to increase, and further reduction in cost is required. An object of the invention is to provide a structure of an IC chip and a process capable of producing at a lower cost. A feature of the invention is to use a metal film and a reactant having the metal film as a separation layer. An etching rate of the metal film or the reactant having metal is high, and a physical means in addition to a chemical means of etching the metal film or the reactant having metal can be used in the invention. Thus, the IDF chip can be manufactured more simply and easily in a short time.