This paper describes the growth of multi-phase carbon nitride films using hot-wire chemical vapor deposition (HWCVD) on (100)-oriented crystalline Si substrates. A mixture of either CH4/NH3, or CH4/N-2 was activated over a hot tungsten filament under varying deposition conditions. The samples were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). AFM micrographs show the presence of facetted crystallites. The XRD peaks observed were compared with theoretical predictions for alpha-C3N4 and beta-C3N4-the two ultra-hard phases of carbon nitride. The results suggest the presence of alpha-C3N4 and beta-C3N4, as well as other unidentified phases in our films. We also calculated the equilibrium concentration of the various gas species as a function of temperature and pressure. Our results indicate that CN and C2N2 radicals are possible precursors to carbon nitride growth. (C) 2003 Elsevier Science B.V All rights reserved.