TiNx diffusion barriers have been deposited onto n‐Si wafers by reactive sputtering in a N2+Ar atmosphere, with a nitrogen content varying in the 0%–25% range. The relative composition of the as‐deposited films was examined by Rutherford backscattering spectroscopy (RBS) and Auger electron spectroscopy (AES) analysis yielding a TiNx composition between x=0.8 and x=1.2, respectively. The near stoichiometric samples were thermally annealed at temperatures between 600 and 900 °C in vacuum and N2 atmosphere. Films with composition TiN1.1 and TiN0.9 present very good behavior as barrier layers against the Si diffusion and a very low reactivity with the Si substrate. When the nitrogen content in the as‐deposited films decreases, the films lose their barrier properties. For the TiN0.8 samples, Si diffusion through the films is observed after annealing in vacuum at temperatures of 600 °C and above. However, when the heat treatment is carried out in a N2 atmosphere an improvement in the barrier characteristics and reactivity with the Si at the interface was observed.