Carbon nitride films with 1 μm thickness were prepared on tungsten carbide (WC) and silicon wafers by Ion Beam and Vapor Deposition (IVD). Films with a composition ratio CR(C/N) = 0.5∼0.7 on WC prepared by nitrogen ions with energies lower than 800 eV showed a hardness of 6500 kgf/mm2which is comparable or greater than that of diamond. The structure of the films is amorphous. For the hardest films, it is considered that all nitrogen atoms are covalently bond to carbon atoms.