Ternary hafnium‐doped tantalum oxide (HfxTayOz) films were successfully obtained after wet oxidation at different temperatures (400‐1000°C). A phase transformation from amorphous to crystalline HfxTayOz phases as well as film densification process happened with respect to temperature until 800°C. However, at temperature beyond 800°C, an increase of the thickness was attained as a consequence of film growth and interfacial layer formation. Besides, additional phenomena allied with nitridation and passivation have also happened in the samples. However, formation of N‐H complex would decrease the nitridation and passivation due to a reduction of nitrogen and H2 available at the interface to retard interfacial layer formation as well as minimizing density, effective oxide charges, and slow trap density demonstrated by HfxTayOz for a functional MOS capacitor were investigated.