PURPOSE: An inertia sensor is provided to be driven in a particular desirable direction by preventing wave propagation to an unwanted direction. CONSTITUTION: An inertia sensor (100) comprises a membrane (110), a mass body (120), a piezoelectric body (130), and a trench (140). The mass body is formed at the lower part of the membrane. The piezoelectric body is formed at the membrane and drives the mass body. The trench is recessed at the piezoelectric body in the direction of the thickness for perpendicularly meeting the driving direction of the mass body.
