SEMICONDUCTOR GAS SENSOR

PURPOSE:To raise the heating effect and to improve the sensitivity and the gas responsiveness by laminating successively a metallic layer having an electric heating function, an insulating layer and a gas sensitive layer and providing a leader line, an electrode and a lead wire on an insulating substrate. CONSTITUTION:On one face of an electric insulating substrate 6, a metallic layer 7 to which a metal such as nichrome, etc., having an electric heating function has been vapor-deposited, a leader line 8 which has been fixed to both end parts 7a of the surface of the layer 7, an insulating layer 9, an electrode 10 provided on both end parts of the surface of the layer 9, a lead wire 11 connected to the electrode 10, and a gas sensitive layer 12 are formed successively. In this state, when a DC or AC voltage is applied to the leader line 8, the metallic layer 7 becomes a plane heater, and by heating uniformly the gas sensitive layer 12 through the insulating layer 9 by thermal conduction, gas is adsorbed uniformly to the layer 12. By measuring a resistance value through the electrode 10 and the lead wire 11, gas concentration is detected from a variation of an electric resistance of the layer 12.