A new microelectronic gas sensor utilizing polycrystallinediamondfilm in conjunction with a catalytic metal has been developed for hydrogen detection. The sensor is fabricated in a layered Pd/i-diamond/p-diamond metal-insulator-semiconductor (MIS) Schottky-diode configuration on a tungsten substrate. The performance of the sensor for H2 detection has been examined in the temperature range 27-300°C. The analysis of the steady-state reaction kinetics has confirmed that the hydrogen adsorption process is responsible for the barrier-height change in the diamond-based MIS Schottky diode. The use ofdiamond-film technology opens the door to the development of a microelectronic gas sensor that can operate at a wider and higher temperature range than the ones based on present silicon technology.