Semiconductor dynamic quantity sensor

A semiconductor dynamic quantity sensor comprising:

• a first capacitance constituent portion having a laminate substrate including a thin film semiconductor layer disposed through insulating film on a support substrate formed of a semiconductor material, a first beam arrangement structure sectionally formed in the thin film semiconductor layer, and a first movable electrode portion of the first beam arrangement structure disposed so as to confront the support substrate through a first cavity, the first movable electrode portion being displaced in a direction perpendicular to the surface of the support substrate under action of a dynamic quantity while a first carrier voltage is applied to the first movable electrode portion to thereby vary a first capacitance between the movable electrode portion and the support substrate;
• a second capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first capacitance constituent portion, and has a second beam arrangement structure sectionally formed in the thin film semiconductor layer, and a second movable electrode portion of the second beam arrangement structure disposed so as to confront the support substrate through a second cavity, the second movable electrode portion being displaced in a direction perpendicular to the surface of the support substrate under action of the dynamic quantity while a second carrier voltage is applied to the second movable electrode portion, whereby a second capacitance between the second movable electrode portion and the support substrate being varied in a variation state different from the variation state of the first capacitance based on the displacement of the first movable electrode portion of the first beam arrangement structure, and a differential capacitance between the first capacitance and the second capacitance being output to the support substrate;
• a third capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first and second capacitance constituent portions, and has a signal output counter electrode sectionally formed in the thin film semiconductor layer while the insulating film exists below the signal output counter electrode portion, the differential capacitance being output by the signal output counter electrode portion;
• a C-V conversion circuit for converting to a voltage signal the differential capacitance output by the signal output counter electrode portion of the third capacitance constituent portion;
• and
• a self-diagnosis fixed capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first, second and third capacitance constituent portions, has a voltage applying counter electrode portion sectionally formed in the thin film semiconductor layer while the insulating film exists below the voltage applying counter electrode portion and forcedly changes the potential of the support substrate, wherein
• the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion under self-diagnosis is set to a first potential, and the signal output counter electrode portion of the third capacitance constituent portion is set to a second potential different from the first potential to forcedly change the potential of the support substrate serving as a fixed electrode of the first and second capacitance constituent portions, whereby the first and second movable electrodes of the first and second capacitance constituent portions are displaced by electrostatic force.