PURPOSE: To suppress sublimation of a sublimatable element from a metal oxide semiconductor with an exhaust gas sensor for which the metal oxide semiconductor is used by providing a sublimation source contg. the same element as the sublimatable element of the metal oxide semiconductor.

CONSTITUTION: The metal oxide semiconductor 4 is housed in a cavity 12 provided on the front end of a heat resistant insulating substrate 2. A pair of electrodes 14, 16 are embedded in the metal oxide semiconductor 4 and the entire surface or part of the metal oxide semiconductor 4 is coated with the material which contains the same element as the sublimatable element contained in the metal oxide semiconductor 4 and has the vapor pressure larger than the vapor pressure of the metal oxide semiconductor 4, as the sublimation source 24. The sublimation of the element from the metal oxide semiconductor 4 is thereby suppressed and the deterioration of the exhaust gas sensor is prevented.