In this work, we discuss the electrical characteristics of metal–insulator–metal (MIM) structures based on ultra-thin hafnium oxides whose stoichiometry have been modified and a thermal treatment after gate metallization has also been applied. Here, we show that the current–voltage characteristics are improved for the annealed samples in terms of lower gate leakage current densities and higher breakdown electric fields. In addition, the role of the modulation in the oxygen concentration for HfO2 on the MIM's current–voltage, capacitance–voltage, and resistive switching characteristics is also addressed. From these data, a trade-off between current–voltage characteristics and basic memory performance is clearly seen, thus highlighting the importance of combining oxygen modulation and/or post-metallization annealing in HfO2-based MIM structures. Finally, the resistive switching effect is shown in the bipolar mode for some MIM structures and the dominant carrier conduction mechanism (just before the SET condition) is also obtained and related to Poole–Frenkel conduction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim