Patent ID: 7096732

Claim:
A semi conductor device, comprising: a circuit substrate; a conductive substrate; an insulation film disposed on said conductive substrate; a semiconductor substrate including a movable portion that may be vibrated in a first direction; an input electrode disposed on said insulation film so as to face said movable portion through an open space, receiving periodic signal from said circuit substrate, and causing said movable portion to vibrate in said first direction, a first stray capacitor of a first capacitance being induced in said insulating film between said input electrode and said conductive substrate; an output electrode disposed on said insulation film so as to face said movable portion through an open space, and outputting vibration signal indicating vibration of said movable portion in a second direction, a second stray capacitor of a second capacitance being induced in said insulating film between said out electrode and said conductive substrate, a noise derived from the periodical signal being added to the vibration signal based on the first and second stray capacitors; a dummy electrode disposed on said insulation film so as to induce a third stray capacitor of a third capacitance in said insulating film between said dummy electrode and said conductive substrate in a manner that the third capacitance is substantially equal to the second capacitance induced by the output electrode, a dummy signal being generated in said dummy electrode from the periodical signal received in said input electrode based on the first and third stray capacitors; and a noise reducer which reduces the noise in the vibration signal by using the dummy signal of said dummy electrode.