Nearly ’’stoichiometric’’ amorphous silicon carbide films were prepared by the reactive sputtering of a silicon target in a gaseous mixture of Ar, CH4, and H2(or D2). The use of the1H (11B, &agr;)&agr;&agr; nuclear reaction and infrared transmission measurements shows that controlled amounts of hydrogen can be incorporated in the films during deposition. The hydrogen content has a dominant effect on the density of the films, its optical gap, and its refractive index. The films could be well described as a polycarbosilane, made of CHn, SiH, and SiC groups. Moreover,11B bombardment induces a decrease of the hydrogen content and a drastic change in the bonds of the polycarbosilane. In conclusion, we show that reactive sputtering is an alternative to the glow discharge technique previously described by W.E. Spear to obtain amorphous silicon carbide.