There are disclosed a semiconductor device in which a short circuit between an oscillator and a semiconductor substrate is prevented, the semiconductor device being capable of suppressing an increase of fabrication steps, and a method of fabricating the semiconductor device. The semiconductor device includes: a semiconductor substrate, in which a recessed portion is formed on an upper surface, and a semiconductor layer is exposed to a bottom surface of the recessed portion; an oscillator that has a beam-type movable electrode arranged in the recessed portion, the movable electrode having insulating films arranged on side surfaces and lower surface thereof, and is fixed to the semiconductor substrate at a position apart from the movable electrode; and a beam-type fixed electrode that is arranged in the recessed portion so as to be opposed to the movable electrode, and is fixed to the semiconductor substrate so as to be electrically isolated from the movable electrode.