Patent ID: 8132458

Claim:
An acceleration sensor formed of an SOI substrate of a three-layered structure including a silicon layer (active layer silicon), a silicon oxide layer, and a silicon layer (substrate silicon), the acceleration sensor comprising: a frame part; a plurality of beam parts, the beam parts projecting inward from the frame part; and a weight part supported by the beam parts; wherein: each of the beam parts is provided with a strain sensing part; and a width W of each of the beam parts, a length I of each of the beam parts, and an inner frame length L of the frame part satisfy the following relationships of Expressions (1) and (2) 2< L/I ≦ 2.82 Expression (1) I/W≦ 3.68 Expression (2) wherein the weight includes: a weight bonding part integrally formed with the beam parts; and a weight having a weight base part supported by the weight bonding part, and projecting parts projecting outward from the weight base part; and a thickness of the weight is between 300 μm and 800 μm, and a clearance between the projecting parts and the frame part is between 70 μm and 110 μm.