In this work hafnium oxide (HfO 2 ) was deposited by r.f. magnetron sputtering at room temperature and then annealed at 200 1C in forming gas (N 2 +H 2 ) and oxygen atmospheres, respectively for 2, 5 and 10 h. After 2 h annealing in forming gas an improvement in the interface properties occurs with the associated flat band voltage changing from Γ2.23 to Γ1.28 V. This means a reduction in the oxide charge density from 1.33 Γ 10 12 to 7.62 Γ 10 11 cm Γ2 . After 5 h annealing only the dielectric constant improves due to densification of the film. Finally, after 10 h annealing we notice a degradation of the electrical film's properties, with the flat band voltage and fixed charge density being Γ2.96 V and 1.64 Γ 10 12 cm Γ2 , respectively. Besides that, the leakage current also increases due to crystallization. On the other hand, by depositing the films at 200 1C or annealing it in an oxidizing atmosphere no improvements are observed when comparing these data to the ones obtained by annealing the films in forming gas. Here the flat band voltage is more negative and the hysteresis on the C-V plot is larger than the one recorded on films annealed in forming gas, meaning a degradation of the interfacial properties.