Amorphous SiC:H (a-SiC:H) films were produced by means of plasma-polymerizing of hexamethyldisilazane (HMDSN) in a radio frequency discharge apparatus at various discharge powers and substrate temperatures. These films were characterized in terms of Young’s modulus, internal stress and strain. The chemical bonding nature of the films was investigated by measuring infrared (IR) absorption spectra. The IR absorption spectra indicate that the films deposited at low discharge powers and room temperature contain Si-CH3, C-H, Si-C, and Si-N-Si bonds of the monomer, and a new bond Si-H. The density of the hydrogen-containing bonds decreased rapidly with increasing discharge power via the decomposition of methyl groups. This decomposition leads to the increase in the density of cross-links of the films. Elevated substrate temperatures accelerate the decomposition rate of the bonds at the same discharge power. As a result, Young’s modulus and internal stress of the films increased with the discharge power and the substrate temperature. The internal strain calculated from Young’s modulus and internal stress, however, decreased with the discharge power. These mechanical properties are closely related to hydrogen density, or atomic fraction of hydrogen in the films.