Three axes accelerometer

A three axis accelerometer comprising:

• a semiconductor substrate;
• a first layer of conductive material formed on the substrate and generally defining a plane;
• a second layer of conductive material mounted by a plurality of flexible arms each having a first end attached to a center post supported on the substrate and a second end attached to support the second layer and with a major surface of the second layer in spaced relation from the first layer and parallel to the plane for limited movement relative to the first layer;
• a third layer of conductive material supported on the substrate and fixedly mounted relative to the first layer and parallel to the plane, the third layer being mounted adjacent and in spaced relation from a second major surface of the second layer;
• the first and second layers forming a first capacitance and the second and third layers forming a second capacitance, each formed capacitance varying in accordance with acceleration of the accelerometer along a first axis defined by the first, second and third layers;
• conductive plates formed as a portion of the first layer and a portion of the third layer and electrically isolated conductive surfaces formed as a portion of the second layer, the various conductive plates being positioned in juxtaposition with the conductive surfaces formed as a portion of the second layer moveable with the second layer, relative to the first and third layers, the surfaces and plates being further formed to define second and third axes mutually orthogonal with each other and the first axis;
• and
• variable capacitances being formed between the various conductive surfaces and conductive plates which variable capacitances vary in accordance with acceleration in the second and third axes.