WxN is a promising candidate as a barrier material for Cu metallization. In this work, we report: the characterization of WxN films deposited by plasma enhanced chemical vapor deposition using WF6/N-2/H-2 gas mixtures. The films are analyzed by Rutherford backscattering spectrometry, Auger electron spectroscopy, atomic force microscopy, x-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and sheet resistance combined with thickness measurements. The diffusion barrier properties are studied by using Cu-gate metal-oxide-semiconductor capacitors and subjecting to either bias-temperature stress. (BTS) of 2 Mv/cm at 250 degrees C or thermal anneal up to 700 degrees C, and evaluated by capacitance-voltage measurement. It is found that the as-deposited films with W/N ratios from 2-19 have an "amorpbous-like" nature. Study of the initial growth shows that the WxN films form by nucleation and grow through coalescence, and the films exhibit a granular structure. The transformation from the amorphous-like structure to crystalline phase(s) depends on the Blm stoichiometry. For the W/N similar to 2 films, there are two transformations starting at 497 and 578 degrees C (at a heating rate of 10 degrees C/min), corresponding to the formation of the W2N phase and to the further growth of the phase together with the formation of a small amount of alpha-W, respectively. The corresponding activation energies are 2.20 and 2.98 eV. For the W/N similar to 3 films, there is only one transformation (to the W2N+ alpha-W) starting at 601 degrees C and with an activation energy of 2.94 eV. The resistivity is found to be insensitive to the film stoichiometry when the film has an amorphous-like nature, but shows a larger decrease for W richer films upon annealing at 500 degrees C. Moreover, for W/N similar to 2 and 3 films, the resistivities are largely determined by the film thickness, from about 200 mu Ohm cm for the 120 nm films to 310-350 mu Ohm cm for the 10 nm films. BTS results reveal that. 10 nm of the W/N similar to 3 barrier shows no sign of degradation at least up to 105 h. By contrast, it is found that the initial barrier degradation occurs by annealing at 600 degrees C and above. This is probably due to the formation of alpha-W grains in the WxN barrier at these temperatures.