Patent ID: 7503507

Claim:
A wireless IC tag comprising an IC chip, wherein the IC chip has a SOI structure comprising a silicon sheet layer, a silicon device layer, and a silicon oxide layer formed between the silicon sheet layer and the silicon device layer, and comprises a capacitance detection circuit, a digital conversion circuit, a transmission circuit formed on the silicon device layer, and a capacitive element formed between a wiring layer and a rubber-like elastic material, wherein the capacitive element comprises a pair of wirings at least one of which contacts the silicon oxide layer, and a gap formed between the pair of wirings, wherein an aperture which reaches the silicon oxide layer is formed on the silicon sheet layer on a lower side of the capacitive element and filled with the rubber-like elastic material bulging from a surface of the silicon sheet layer, and wherein a change in a capacitance value of the capacitive element is detected by the capacitance detection circuit connected to the capacitive element, the detected change in the capacitance value is converted to a digital value by the digital conversion circuit, and the digital value is transmitted from the transmission circuit to outside.