Crystalline carbon nitride films have been synthesized on Si (100) substrates by a microwave plasma chemical vapour deposition technique, using mixture of N2, CH4 and H2 as precursor. Scanning electron microscopy shows that the films consisted of hexagonal bars, tetragonal bars, rhombohedral bars, in which the bigger bar is about 20 μm long and 6 μm wide. The X-ray photoelectron spectroscopy suggests that nitrogen and carbon in the films are bonded through hybridized sp2 and sp3 configurations. The x-ray diffraction pattern indicates that the films are composed of α-, β-, pseudocubic and cubic C3N4 phase and an unidentified phase. Raman spectra also support the existence of α- and β-C3N4 phases. Vickers microhardness of about 41.9 GPa measured for the films.