A semiconductor substrate of a semiconductor device has a sensor region and an integrated circuit region, and a cavity is formed immediately under a surface layer portion of the sensor region. A capacitive acceleration sensor is formed on the sensor region by working a surface layer portion of the semiconductor substrate opposed to the cavity. The capacitive acceleration sensor includes an interdigital fixed electrode and an interdigital movable electrode. A CMIS transistor is formed on the integrated circuit region. The CMIS transistor includes a P-type well region and an N-type well region formed on the surface layer portion of the semiconductor substrate. A gate electrode is opposed to the respective ones of the P-type well region and the N-type well region through a gate insulating film formed on a surface of the semiconductor substrate.