METAL OXIDE SEMICONDUCTOR GAS SENSOR

PROBLEM TO BE SOLVED: To provide a metal oxide semiconductor gas sensor exhibiting an extremely high sensitivity and insusceptible to aging. SOLUTION: Using an induction plasma thermal spray equipment 20 comprising a pressure reducing tank 21 incorporating a thermal insulation plate 22 for mounting a substrate 10 on which an electrode 15 is formed and a plasma torch 24 coupled with the pressure reducing tank and including a powder introduction probe 26 and a high frequency coil 25, the substrate is mounted on the thermal insulation plate, a gap of 1,000 mm or less is set between the substrate side forward end of the powder introduction probe and the substrate, metal oxide powder is supplied from the powder introduction probe while reducing pressure in the pressure reducing tank and generating high frequency induction plasma from the high frequency coil, and a metal oxide comprising multiple large particulate parts formed on the surface of the substrate and small particulate parts formed on the circumferential surface of the large particulate parts is deposited thus obtaining a metal oxide semiconductor gas sensor.