PURPOSE: To increase an adhesive property to a substrate of a semiconductor layer and also, to improve sensitivity of detecting gas by forming the metallic oxide semiconductor layer on the insulating substrate attached an electrode and covering a porous film on the surface and surroundings.

CONSTITUTION: A metallic oxide semiconductor layer 4 essentially consisting of stannic oxide is formed on an insulating substrate 1 attached on electrode 2 by a thick film printing method and is calcined. A glass layer 5 containing a metallic oxide semiconductor material e.g. 1W20wt% stannic oxide is formed by printing on noncrystallized glass consisting of 40wt% B2O3, 46wt% SiO2 and 4wt% Al2O3 and is calcined at transition temperature of the glass or more. The adhesive property to the insulating substrate 1 of the semiconductor layer 4 is improved without obstructing the permeability of gas to the semiconductor layer 4 because the glass layer 5 is made porous to a degree to permeate the gas.