Crystalline carbon nitride films have been synthesized on Si substrates by microwave plasma chemical vapor deposition technique, using a gas mixture of nitrogen and methane. Scanning electron microscopy shows that the film consisted of hexagonal crystalline rods. X-ray diffraction and transmission electron microscopy indicate the films are mainly composed of α-and β-C3N4, and these results match more closely with α-C3N4 than with β-C3N4 phase. Fourier transform infrared (FTIR) and Raman spectra of carbon nitride were calculated through Hooke's law. The observed FTIR and Raman spectra support the existence of α- and β-C3N4 in the films.