Motorola Corporation

Barun K Kar

Eric D Joseph

Guang X Li

Zuoying Lisa Zhang

Ronald J Gutteridge

Frank A Shemansky, Jr

A sensor (100) includes a fixed gate field-effect transistor (138) that produces a quiescent signal (V.sub.QUIESC1) in a channel (336) when a control signal (V.sub.CONTROL) is applied to a source (332) of the FGFET. A movable gate field-effect transistor (MGFET) (108) produces a sense signal (V.sub.ACCEL) in a channel (316) in response to a physical condition of the sensor when the control signal is applied to a source (312) of the MGFET such that the sense signal is proportional to the quiescent signal. The difference between the currents in the FGFET and MGFET is amplified by a differential amplifier (230) to produce the output signal (V.sub.OUT) of the sensor. The difference between a reference signal (V.sub.RATIO) and the quiescent signal is amplified in an amplifier (206) to produce the control signal that adjusts the output signal to be proportional to the reference signal.

Transducer and interface circuit

A semiconductor device (15) having a sensor (11) and a transistor (10) formed on a monolithic semiconductor substrate (16). The sensor (11) has a source region (41), a drain region (42), and a microstructure (12) which is formed from a conductive layer (28). The microstructure (12) modulates a channel region between the source and drain regions (41,42). The transistor has a gate structure, a portion of which is formed from the same conductive layer (28) used to form the microstructure (12). Anneal steps are performed on the conductive layer (28) to remove stress prior to the formation of source and drain regions (34,36) of the transistor (10). A self-test structure (14) is formed adjacent to the microstructure (12) which is used to calibrate and verify the operation of the sensor (11).

Monolithic semiconductor device having a microstructure and a transistor

Converting a Coriolis force into an electrical signal, an electro-mechanical transducer (10) is a field effect transistor (18) having angular velocity sensing capabilities. A gate electrode (16) is suspended over a channel region (60) of a substrate (31), is biased at a desired potential, and is oscillated along an axis (40). The gate electrode (16) and the substrate (31) are rotated about a different axis (41) at an angular velocity (44). The resulting Coriolis force displaces the suspended gate electrode (16) along yet another axis (42) which modulates a current (53) in the channel region (60) of the substrate (31). The amplitude of the current (53) describes the magnitude of the angular velocity (44).

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Tempe, AZ, United States of America

Barun K Kar