Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, in which an active layer is located on a supporting substrate with an insulating intermediate layer therebetween and a movable unit included in the active layer moves in relation to the supporting substrate in response to a force applied to the movable unit, wherein the force is correlated to a dynamic quantity to be measured by the device, the method comprising steps of:

• forming an SOI substrate that includes a semiconductor substrate, an insulating layer, and a semiconductor layer such that the insulating layer is located between the semiconductor layer and the semiconductor substrate;
• dry etching the semiconductor layer to form a trench that extends through the semiconductor layer to the insulating layer;
• dry etching a sidewall defining the trench at a portion adjacent to a bottom of the trench to form a movable unit, wherein the later dry etching is implemented with a charge building up on a surface of the insulating layer that is exposed during the former dry etching such that etching ions strike and etch the portion of the sidewall and wherein the later dry etching is implemented at an etching rate higher than that at which the former dry etching is implemented to reduce the deposition amount of a protection film that is deposited on a reverse side of the movable unit during the later dry etching.