Patent ID: 9674618
Date: 2017-06-06
CPC Classifications: H04R,H04S

Claim:
1. An acoustic sensor that detects acoustic vibration by converting the acoustic vibration into change in electrostatic capacitance between a vibration electrode film and a fixed electrode film, comprising: a semiconductor substrate having an opening in a surface thereof; a back plate composed of a fixing plate and the fixed electrode film provided on the fixing plate, the fixing plate being arranged to face the opening of the semiconductor substrate and having a plurality of sound holes and the fixed electrode film provided on the fixing plate; and the vibration electrode film arranged between the back plate and the semiconductor substrate so as to face the back plate across a gap, wherein the fixing plate is provided by a semiconductor manufacturing process, and a frame wall is constituted with a curved shape in at least a portion of a periphery of the fixing plate, the frame wall being coupled directly or indirectly to the semiconductor substrate, and a sacrifice layer removed from an inner side of the fixing plate in the semiconductor manufacturing process remains at least on a portion of an inner side of the frame wall, with roughness of an inward surface of the remaining sacrifice layer being smaller than roughness of a sound hole shape reflecting structure in which a shape similar to an external shape of the sound holes is repeated, the roughness of the sound hole shape reflecting structure being formed in a case of removing the sacrifice layer using an etching liquid supplied from the plurality of sound holes in the semiconductor manufacturing process.