VOX film, wherein X is greater than 1.875 and less than 2.0, and a bolometer-type infrared sensor comprising the VOX film

At a heat treatment temperature in a reducing atmosphere of Ar and H2, a precursory film of V2 O5 is reduced into a VOx film with the heat treatment temperature selected in a predetermined temperature range between 350 ° C. and 450° C., both exclusive, to control a resistivity of the VOx film, where x is greater than 1.875 and less than 2.0. The VOx film is not susceptible to a metal-semiconductor phase transition inevitable in VO2 at about 70° C. and is excellent for use in a bolometer-type infrared sensor. When reduced at 350° C. and 450° C. the resistivity and its temperature coefficient of the VOx film at room temperature are 0.5 and 0.002 Ω cm and -2.2% and 0.2% per degree Celsius.