a pressure sensor system involves a semi - conductive diaphragm electrode overlying a cavity in a semiconductor chip , with the center of the diaphragm secured to a mesa extending upwardly from the cavity . a second electrode is implemented by a heavily doped raised ring between the mesa and the periphery of the chip at the ring of maximum deflection of the diaphragm . the raised ring electrode is heavily doped with one polarity , with light doping near the base of the raised area , and the remainder of the cavity is heavily doped with the opposite polarity . the plot of linearity error versus width of the ring electrode , has a minimum , and the width of the ring electrode and related constructional features are selected to conform to the minimum point of the linearity function . the reference capacitor is arcuate in configuration and extends part way around and in immediate proximity to the sensor diaphragm .