A semiconductor pressure sensor utilizes single-crystal silicon piezoresistive gage elements dielectrically isolated by silicon oxide from other such elements, and utilizes an etched silicon substrate with an etch stop. P-type implants form p-type piezoresistive gage elements and form p+ interconnections to connect the sensor to external electrical devices. The diaphragm is made from epitaxially-grown single-crystal silicon. Passivation nitride can be used for additional dielectric isolation. One practice of the invention provides over-range cavity protection, and thus increased robustness, by forming an over-range stop for the diaphragm through localized oxygen ion implantation and etching.