To provide a semiconductor acceleration sensor of which electrostatic self-diagnosis sensitivity and damping characteristics can be set precisely.

The semiconductor acceleration sensor is provided with a semiconductor substrate 1 on which a movable part is formed of a weight part 3 and a beam part 2, a conductor electrode 9 disposed oppositely to the bottom face of the weight part 3 through a microgap 7, and a base 4 for supporting the conductor electrode 9. The size of the conductor electrode 9 on the side facing the bottom face of the weight part 3 is set smaller than the size of the bottom face of the weight part 3. Although the facing area depends on the size at the facing part of the conductor electrode 9 having smaller dimensions than the bottom face of the weight part 3, the size at the facing part can be set by the groove part 8 in the base 4 which can be set precisely. Consequently, the facing area can be set precisely regardless of fluctuation in the size of the bottom face of the weight part 3 and thereby, the electrostatic self-diagnosis sensitivity and the damping characteristics can be set precisely.