Patent ID: 7201053

Claim:
A capacitance type physical quantity sensor for detecting physical quantity, the sensor comprising: a movable portion including a movable electrode; a fixed portion including a fixed electrode; and a substrate, wherein the movable electrode includes a detection surface, wherein the fixed electrode includes a detection surface facing the detection surface of the movable electrode, wherein the movable electrode is movable toward or against the fixed electrode in accordance with the physical quantity applied to the sensor so that a distance between the detection surfaces of the movable and the fixed electrodes is changeable, wherein at least one of the movable and the fixed electrodes includes a groove, wherein the groove is disposed on a top or a bottom of the one of the movable and the fixed electrodes, has a predetermined depth from the top or the bottom, and extends across from the detection surface of the electrode to an opposite detection surface of the same electrode so that a direction that the groove extends is parallel to a movable direction of the movable electrode, wherein the movable portion further includes a spring and a massive portion, wherein the fixed portion further includes an anchor, wherein the movable portion is supported on the substrate through the spring, wherein the massive portion together with the movable electrode is displaceable in accordance with the physical quantity applied to the sensor, wherein the movable electrode is integrally disposed on a side of the massive portion to extend from the massive portion, wherein the fixed electrode extends from the anchor so that the fixed electrode is supported on the substrate through the anchor, wherein the detection surface of one or more of the movable electrode and the fixed electrode is perpendicular to the movable direction, and wherein the sensor detects the physical quantity on the basis of a change of a capacitance provided by a capacitor between the detection surfaces of the movable and the fixed electrodes, the change of the capacitance caused by a displacement of the movable electrode in accordance with the physical quantity applied to the massive portion.