An acceleration sensor capable of standing a great acceleration is to be provided. It is configured of a mounting board and a sensor chip in which the sensor chip is formed of a weight, a beam and a frame. Then, the weight is surrounded by the frame. The weight is joined to the frame by a plurality of the beams, and the weight is separated from the board by being supported by the beams. Additionally, a thin, rectangular stopper is disposed on the mounting board right under the weight.
A disclosed semiconductor sensor includes a proof-mass, a frame disposed around the proof-mass and including at least a silicon layer, a beam for supporting the proof-mass, the beam being disposed at a first surface side of the frame between the proof-mass and the frame, a piezoresistor disposed on the beam, a metal wiring pattern and a pad electrode formed on the first surface of the frame and electrically connected to the piezoresistor, a cover plate disposed above and spaced apart from the proof-mass and the beam at the first surface side of the frame and fixed to a cover plate fixing area disposed on the first surface of the frame, and a projection disposed on the proof-mass at the first surface side to prevent the proof-mass from sticking to the cover plate.
