Patent ID: 7028551

Claim:
A pressure sensor system comprising: a semiconductor chip; a diaphragm constituting a first electrode, formed on said chip; said diaphragm being formed of semi-conductive material; said diaphragm facing a cavity in said chip with a second electrode in the form of a doped semiconductor raised area facing said diaphragm; said first and second electrodes constituting a sensing capacitor with a capacitance that varies with deflection of said diaphragm; a reference capacitor formed on the surface of said chip in an arcuate configuration adjacent said diaphragm, said reference capacitor having a capacitance in the same order of magnitude as said sensing capacitor; said cavity having a raised mesa secured to the center of said diaphragm; said second electrode being substantially in the form of a raised ring extending around said mesa, and with said raised ring located between said mesa and the periphery of the diaphragm; said semiconductor chip having a p-n junction substantially at the base of the raised ring forming the second electrode; circuitry formed on said chip for converting capacitance variations of said diaphragm relative to said reference capacitor, to a substantially linear output with changes in pressure applied to said diaphragm; and bonding pads mounted on said chip to receive leads for coupling to external circuitry.