The sensor response behavior of the Ru/3C-SiC (epilayer on Si substrate) Schottky junctions was studied at different temperatures in presence of hydrogen gas with concentrations varying from 5,000 ppm to 20,000 ppm. The output signal of the sensors, the response time, and the reversibility were investigated from the transient response characteristics of the sensors. The sensor parameters were found to improve with higher operating temperature, up to 400°C, above which they degrade due to the influence of thermally generated carriers in the Si substrate. The sensitivity was found to be a function of applied bias across the junction. As compared to the Pd/3C-SiC junctions, the Ru/3C-SiC Schottky sensors showed better resolution in the hydrogen concentration range between 10,000 and 20,000 ppm. Also, the Ru/3C-SiC sensors showed better reversibility. The secondary ion mass spectrometry study indicates that the Ru/3C-SiC Schottky sensors can be operated at 400°C without any significant degradation of the interface.