Abstract: A method for producing a transistor-type hydrogen sensor is invented. This method combines conventional semiconductor fabrication process with an electroless plating technique. The fabrication process comprises steps as follows: (a) preparing a semiconductor substrate, (b) forming a semiconductor-based material with an exposed surface on the substrate, (c) washing and then drying the semiconductor-based material, (d) separating the exposed surface of the semiconductor-based material, (e) depositing a gold-germanium alloy on the semiconductor-based material to form two Ohmic contacts, and (f) forming a Schottky contact gate metal having an affinity for hydrogen. The electroless plating technique deposits the Schottky contact gate metal, having an affinity for hydrogen, at a relatively low temperature and it thus can produce a transistor-type hydrogen sensor with excellent sensing performances.