Infrared sensor manufactured by method suitable for mass production

A bolometer-type infrared sensor that changes a temperature of a light-incident portion thereof by absorption of incident infrared light so as to change an electrical resistance value of a resistor by a temperature change, thereby outputting a signal indicative of a radiation intensity of the incident infrared light, the method comprising:

• a substrate;
• an infrared reflecting film formed on the substrate;
• a bridge structure comprising an insulating film and formed on the substrate to cover the infrared reflecting film;
• an bolometer resistor film made of vanadium oxide and formed on the insulating film;
• the bolometer resistor film having a first surface in contact with the insulating film and a second surface on the side opposite of the first surface, varying in film structure from crystal structure to amorphous structure towards the second surface from the first surface, and reducing in an amount of oxygen towards the second surface from the first surface, and
• a protective layer formed on the bridge structure and covering the bolometer resistor film.