Patent ID: 7563724

Claim:
A method of producing a semiconductor pressure sensor, the sensor having a diaphragm to be deformed by pressure, comprising: preparing a semiconductor substrate having front and rear surfaces, both of the surfaces being mirror surfaces, the semiconductor substrate being a single layer; forming a thermally-oxidized film on the rear surface of the single layer semiconductor substrate; forming a detecting part in the front surface of the single layer semiconductor substrate, the detecting part comprising a gauge resistance layer; forming an etching mask on the rear surface of the single layer semiconductor substrate, the etching mask comprising the thermally-oxidized film; etching the single layer semiconductor substrate from its rear surface with the etching mask without going through the single layer semiconductor substrate to form a concave portion, the concave portion having a bottom portion functioning as a diaphragm, forming a nitride film on the thermally-oxidized film disposed on the rear surface of the single layer semiconductor substrate after forming the thermally oxidized film; and removing the nitride film on the thermally-oxidized film and forming a plasma nitride film instead of the nitride film after forming the detecting part, wherein the forming of the etching mask comprises forming a two-layer etching mask made of the thermally-oxidized film and the plasma nitride film.