Silicon carbide nanocrystals embedded in a SiO2 matrix on monocrystalline Si substrates were prepared by radio frequency (RF) co-sputtering with Si, C and SiO2 targets, and subsequent high-temperature annealing. The structure of the films was determined by Fourier transform infrared spectroscopy. Photoluminescence (PL) from the composite films was studied as a function of annealing temperature. It was found that the PL spectra of the films are very sensitive to the annealing temperature. Blue band (490 nm) and green band (~546 nm) visible PL, originating from SiC nanoparticles and C nanoclusters, respectively, were observed at room temperature.