Abstract: A sound hole is provided in a silicon substrate. A diaphragm electrode is secured to the upper surface of the silicon substrate via at least one fixed end so as to cover the sound hole of the silicon substrate. The diaphragm electrode is provided with four projections extending in respective directions of diameter orthogonal to each other. The fixed end is provided in one of the four projections. Hinge shafts are provided in the other three projections. A backplate electrode is provided above the diaphragm electrode so as to form a capacitor.

Abstract: A sound hole is provided in a silicon substrate. A diaphragm electrode is secured to the upper surface of the silicon substrate via at least one fixed end so as to cover the sound hole of the silicon substrate. The diaphragm electrode is provided with four projections extending in respective directions of diameter orthogonal to each other. The fixed end is provided in one of the four projections. Hinge shafts are provided in the other three projections. A backplate electrode is provided above the diaphragm electrode so as to form a capacitor.

Abstract: When a plurality of through holes is formed in a interlayer dielectric film including Si, O, and C at least, a plurality of dummy through holes is formed in the circumference of a cluster of through holes and an isolated through hole. And/or the etching-gas with a higher content of a nitrogenous gas is used, and the etching is performed step by step using the etching gases containing C4F6 and not containing C4F6. And/or the carbon content ratio in the etching gas defined by p=X×(Qc/Q)×100 where X is a carbon component ratio X in a fluorocarbon gas represented by CXFY, Q is a total flow rate of the etching gas, and Qc is a gas flow rate of fluorocarbon CXFY, is set to 5% or less.