Patent ID: 7337670

Claim:
A semiconductor physical quantity sensor comprising: a substrate having oxide film; a semiconductor layer supported on the substrate; the substrate with the oxide film and semiconductor layer forming a silicon-on-insulator structure; trenches disposed in the semiconductor layer; and a movable portion disposed in the semiconductor layer and separated from the oxide film of the substrate by the trenches, the trenches being disposed at an outer periphery of the movable portion, wherein: the movable portion faces the oxide film of the substrate, the movable portion includes through-holes, each of which penetrates the semiconductor layer in a thickness direction, the movable portion is displaceable on the basis of a physical quantity applied to the movable portion so that the physical quantity is detected by a displacement of the movable portion, and one of the through-holes in the movable portion or one of the trenches disposed at the outer periphery of the movable portion has a width permitting a maximum etching rate of an area of the semiconductor layer adjacent thereto.