In this work, we have prepared the buried SiC layers by a metal vapor vacuum are (MEVVA) ion source, respectively, on Si(100) and surface oxidized Si(100) wafers. The Fourier transform infrared spectroscopy (FTIR) spectra of the buried layers were found to be composed of two components, one assigned to amorphous SiC (a-SiC) and the other one to cubic SiC (beta-SiC). It was found that there is a critical dose at which the relative amount of beta-SiC increase abruptly, and the silicon oxide thickness dependence of the fraction ratio (the relative amount of beta-SiC/the relative amount of a-SiC) in the buried layers is of the shape similar to the distribution of the carbon content. The results indicate that in the region of the maximum carbon content the crystallized degree of the buried layers is higher.