Polycrystalline and amorphous Si‐C films were prepared by rf glow‐discharge decomposition of silane‐methane mixtures at 700 °C. We have demonstrated that polycrystalline SiC films with large grains grow under heavy hydrogen dilution. The bonding properties as a function of film composition and hydrogen dilution were characterized by means of x‐ray diffraction and x‐ray photoelectron spectroscopy. Crystallization takes place at around C contentx=0.5 in Si1−xCx, accompanying some segregation of carbon atoms in grain boundaries, as a result of a preference for heteronuclear bonds. It was shown that C‐C(C3−nSin) (n=0–3) bonds appear in the carbidic phase of C‐rich films, leading to occurrence of compressive strain in the crystalline SiC grains. In addition, effects of hydrogen dilution were discussed in correlation with the strain.