The carbon nitride crystalline thin film formed by N+ implantation into the carbon film deposited on the Si(100) substrate is reported. The hoplanted film was characterized by Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). The RBS result shows the film containing about 70% of C and 30% of N. The XRD spectrum indicates the existence of C-N crystalline phase in the film.