Gas sensor

A gas sensor comprising:

• a first field-effect transistor having a first gate insulation film;
• a second field-effect transistor adjacent to the first field-effect transistor and having a second gate insulation film;
• a first gate electrode on the first gate insulation film and comprising a catalytic metal that causes a dissociation response of hydrogen;
• a second gate electrode on the second gate insulation film, the second gate electrode being coupled to the first gate electrode by wiring, the second gate electrode comprising a non-catalytic metal that does not cause dissociation response of hydrogen, the second gate electrode and the first gate electrode being used to detect hydrogen gas;
• a single voltage applying unit configured to apply to the first gate electrode and the second gate electrode at least one of a direct-current voltage and an alternating-current voltage having a constant voltage difference;
• and
• a differential amplifier configured to measure a differential between the first gate electrode and the second gate electrode,
• wherein the first field-effect transistor and the other field-effect transistor have same structures except that the first gate electrode comprises the catalytic metal and the second gate electrode comprises the non-catalytic metal, so as to compensate the differential between the first field-effect transistor and the second field-effect transistor measured by the differential amplifier.