Tantalum nitride (TaNx) films are deposited on silicon substrates by radio frequency (rf) reactive sputtering of Ta in N-2/Ar gas mixtures. The deposition rate, chemical composition, and crystalline microstructure are investigated by cross-sectional transmission electron microscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction, and atomic force microscopy, respectively. According to those results, the deposition rate, film composition, and microstructure correlate with the bias. A stepwise change in deposition rate is observed at a N-2/Ar flow ratio of 0.2 for all biases. The deposition rate increases with the bias throughout the whole range of N-2/Ar flow ratio. Crystalline TaN can be deposited on Si substrates at a N-2/Ar flow ratio of 0.25 and all biases. The TaN lattice is distorted due to the change of N concentration. In addition, the experimental data which were interpreted using the deposition mechanism and the kinetic model which were published previously.