The oxidation behavior of titanium-nitride (TiN) films, which were formed at different biasing voltages, was investigated, The four film properties investigated (oxygen concentration, electrical resistivity, density, and stress) changed monotonically with the biasing voltage. Two films with extreme biasing conditions, a dense film and a porous film, were used for a detailed investigation of oxidation behavior. The dense film (density equal to bulk) showed a square-root-of-time growth of the oxide layer, and its oxidation rate had an Arrhenius-type temperature dependence with an activation energy of 2.4 eV. The porous film (density 75% of bulk) showed a time-proportional increase in resistivity initially, then saturation. Film composition profiling using Auger electron spectroscopy showed that the initial stage corresponds to fast oxidation and proceeds along the gaps in the film grains; the saturation stage corresponds to the ordinary oxidation process. The oxidation rates for the ordinary process were the same for both films and corresponded to the intrinsic TiN oxidation rate. The fast oxidation rate along the gaps decreased with the oxidation time, corresponding to the so-called stuffing effect.