Patent ID: 7386136

Claim:
A sound detecting mechanism comprising a pair of electrodes forming a capacitor on a substrate in which one of the electrodes is a back electrode forming perforations therein corresponding to acoustic holes and the other of the electrodes is a diaphragm, wherein a multilayered assembly is mounted on the substrate, the multilayered assembly formed of the diaphragm, a sacrificial layer and the back electrode superposed in series by vapor deposition technique; the sacrificial layer is etched relative to the multilayered assembly formed of the diaphragm, the sacrificial layer and the back electrode, thereby defining a void area between the diaphragm and the back electrode, with the sacrificial layer remaining at outer peripheral portions of the void area; and the back electrode being formed by polycrystal silicon of 5 μm to 20 μm in thickness; and the substrate comprises a single crystal silicon on insulator (SOI) structure wafer including a silicon oxide film or a silicon nitride film formed on a monocrystal silicon substrate and a polycrystal silicon film formed on the silicon oxide film or the silicon nitride film.