In a semiconductor acceleration sensor, a weight and thin beam parts adjacent to the weight are formed on a substrate, a moving electrode is formed on the weight, and a fixed electrode is formed at a position of the other substrate opposed to the moving electrode. Both the electrodes come in contact with each other and conduct as a result of acceleration on the weight, whereby the semiconductor acceleration sensor operates. The fixed electrode or the moving electrode is formed with a projection toward the opposed electrode and the projection and the electrode come in contact with each other and conduct by action of acceleration with a predetermined spacing held between both the electrodes for preventing occurrence of chattering caused by the electrostatic attraction force between both the electrodes.