Abstract: The carbon nitride thin films have been prepared on Si substrates, using N,/CH. as reactive gases, by microwave chemical vapor deposition method. The effect of substrate temperature on the composition and structure of carbon nitride thin films were studied by X-ray photoelectron spectroscopy (XPS). As the substrate temperature increased, the N/C atomic ratios increased rapidly first and then decreased a little after a crucial temperature. Fourier transform infrared (FT-IR) and Raman spectra support the existence of C-N covalent bond.