Nanocrystalline films of a ternary compound, namely, silicon carbonitride SiCxNy, are prepared by plasma-enhanced chemical vapor deposition at temperatures of 473–1173 K with the use of a complex gaseous mixture of hexamethyldisilazane Si2NH(CH3)6, ammonia, and helium. The chemical and phase compositions and the physicochemical properties of the films are investigated using IR, Auger electron, and X-ray photoelectron spectroscopy; ellipsometry; synchrotron X-ray powder diffraction; electron and atomic-force microscopy; microhardness measurements with a nanoindenter; and electrical measurements. Correlations of the composition of the initial gas phase and the synthesis temperature with a number of functional properties of the SiCxNy silicon carbonitride films are revealed.