A comparison of two kinds of source materials is made with regard to the growth kinetics of hydrogenated amorphous silicon carbide films using the RF plasma CVD system with parallel electrodes. The two kinds of sources, methyltrichlorosilane and monomethylsilane, are molecules that include one atom each of carbon and silicon. They are used with a hydrogen carrier gas. In the methyltrichlorosilane-hydrogen system, a possible precursor to silicon carbide is SiCl2, and the silicon/carbon ratio of the films can be greatly changed by adjusting the plasma power. In the monomethylsilane-hydrogen system, SiH2 is the rate-determining species, and the silicon/carbon ratio of the films can be slightly changed by adjusting the plasma power. The optical emission spectroscopy (OES) intensity distribution suggests that the precursor in both cases migrates to the substrate from the plasma sheath by diffusion.