A hydrogen gas sensor consisting of planar electrical NiCr contacts formed on the surface of a 3C-SiC epitaxial layer grown on Si(001) has been fabricated and tested. The n-type, 4 mum thick 3C-SiC epi layer was grown under low-pressure conditions with an approximate doping density of 10(18) cm(-3). This sensor demonstrates a two-fold repeatable improvement in stability and sensitivity in comparison to an n-type Si sensor of the same type also fabricated and tested under the same conditions. Both the 3C-SiC/Si and Si sensors operated up to 250 degreesC; however, the 3C-SiC/Si sensor was able to detect hydrogen at concentrations far exceeding that of the Si sensor. The 3C-SiC/Si device detected hydrogen at concentrations ranging from 0.333% to 100% in Ar while the Si sensor could only detect hydrogen at concentrations ranging from 2% to 100% in Ar. Based on this preliminary data, it has been shown that 3C-SiC/Si hydrogen sensors of this type have a larger dynamic range and higher sensitivity to hydrogen than Si sensors, thus allowing for harsh environmental applications.