Significant ion irradiation is needed during growth to synthesize cubic boron nitride(cBN)films. This results in large film stresses, which have limitedcBNfilm thicknesses to only a few hundred nm and represents a significant barrier in the development ofcBNfilm technology. Using a new hybrid deposition technique, we have synthesized cubic BN films up to 700 nm (0.7 &mgr;m) thick. A compositional and structural analysis of the films using several standard characterization techniques confirms that relatively thick polycrystalline films with a highcBNcontent were synthesized. ThickercBNfilms enable hardness measurements to be undertaken without major substrate effects. Nanoindentation measurements yield hardness values for the cubic BN films up to 60–70 GPa, which are greater than values measured for bulkcBN.The measured elastic modulus was observed to be lower than the bulk, and this can be accounted for by an elastic deformation of the silicon substrate. The mechanical properties of the cubic BN films are discussed with reference to other ultrahard thin films such as diamond and diamondlike carbon. ©1997 American Institute of Physics.