This work describes the mechanical properties of a-SiC and a-SiCxNy thin films prepared by RF magnetron sputtering of a SiC target at different N2/Ar gas flow ratios. Four different film compositions were studied. The elastic modulus and hardness of the films were determined by nanoindentation. Fourier transform infrared spectrometry (FTIR), Raman spectroscopy and atomic force microscopy (AFM) were used in order to investigate the influence de nitrogen content on the chemical bonds and morphology of the films.