Abstract: A semiconductor type yaw rate sensor has a substrate, a beam structure formed from a semiconductor material and having at least one anchor portion disposed on the substrate, a weighted portion located above the substrate a predetermined gap therefrom, and a beam portion which extends from the anchor portion and supports the weighted portion. A movable electrode is formed onto the weighted portion, and a fixed electrode is formed on the substrate in such a manner that the fixed electrode faces the movable electrode. When a drive voltage is applied between the movable electrode and the fixed electrode, the beam structure is forcibly caused to vibrate in a direction that is horizontal relative to a substrate surface plane. In this yaw rate sensor, a strain gauge to monitor forced vibration of the beam structure is formed in the beam portion. As a result, the forced vibration of the beam structure can be monitored with a simple structure.

Abstract: A polysilicon thin film is formed on a silicon substrate by LPCVD technique. At this time, by a performing film formation at a low temperature of approximately 620.degree. C., for example, an irregularities portion is formed on the surface thereof. A silicon oxide film that serves as a sacrificial layer is formed thereon and, on this sacrificial layer, a polysilicon thin film that serves as a movable portion forming thin film is formed. Then, the silicon oxide film beneath this polysilicon thin film is removed by wet etching to thereby form a movable portion. As a result, the movable portion of a beam structure that is composed of the thin film is disposed over the silicon substrate at a prescribed distance therefrom. Although an etchant-replacing liquid enters between the movable portion and the substrate whereby the movable portion is attracted toward the substrate, the movable portion is prevented from adhering to the substrate by means of the irregularities portion.