Hafnium oxide (HfO2) used as the gate insulator of metal-insulator-SiC Schottky-diode hydrogen sensors is annealed in nitrogen at different temperatures and durations for achieving a better performance. The hydrogen-sensing properties of these samples are compared with each other by taking measurements under various temperatures and hydrogen concentrations using a computer-controlled measurement system. The sensor response of the device is found to increase with the annealing temperature and time because higher annealing temperature and longer annealing time can enhance the densification of the HfO2 film; improve the oxide stoichiometry and facilitate the growth of an interfacial layer to give better interface quality, thus causing a significant reduction of the current of the sensor under air ambient. The effects of hydrogen adsorption on the barrier height and conduction mechanism of the devices are also investigated. (C) 2010 Elsevier B.V. All rights reserved.