Patent ID: 7004026

Claim:
A capacitance type acceleration sensor comprising: a semiconductor substrate; a weight portion supported with the substrate through a spring portion; a movable electrode integrated with the weight portion; and a fixed electrode cantilevered with the substrate, wherein: the movable electrode together with the weight portion is displaced along with a facing surface of the movable electrode in accordance with acceleration applied to the weight portion, the facing surface of the movable electrode facing a facing surface of the fixed electrode so as to provide a capacitor having a capacitance, the capacitance of the capacitor changes in accordance with a displacement of the movable electrode so that an outer circuit detects the acceleration as a capacitance change, and each facing surface of the movable and fixed electrodes has a concavity and convexity portion for increasing the capacitance change, each of the movable and fixed electrodes has a plurality of teeth, the teeth of the movable and fixed electrodes are disposed alternately so that sidewalls of the teeth provide the facing surfaces, and each concavity and convexity portion of the movable and fixed electrodes has a plurality of convexities and concavities, and the teeth of the movable and fixed electrodes extend in an extending direction, which is parallel to a displacement direction of the movable electrode.