Force detector and acceleration detector and method of manufacturing the same

An acceleration detector detecting an X-axis component and a Y-axis component of an acceleration applied in an XYZ three-dimensional coordinate system, the detector comprising:

• a displacement substrate extending along an XY-plane in the coordinate system,
• a detector casing accommodating the displacement substrate, a periphery of the displacement substrate being supported by the detector casing so that the displacement substrate is caused to be displaced in the detector casing when an acceleration is applied,
• displacement electrodes located on a surface of the displacement substrate,
• fixed electrodes fixed to the detector casing and opposing to the displacement electrodes, respectively, so that capacitance elements are formed, each of said capacitance elements is constituted by a displacement electrode and an opposing fixed electrode,
• a detecting circuit to detect the X-axis component based on a capacitance of a capacitance element among said capacitance elements and to detect the Y-axis component based on a capacitance of another capacitance element among said capacitance elements, and
• a testing circuit to exert a coulomb force between a displacement electrode and a fixed electrode constituting one of said capacitance elements so that a state equivalent to a state where an X-axis component of acceleration is applied can be created without actually applying an acceleration and to exert a coulomb force between a displacement electrode and a fixed electrode constituting another one of said capacitance elements so that a state equivalent to a state where a Y-axis component of acceleration is applied can be created without actually applying an acceleration.