Silicon carbide (SiC) and gallium nitride (GaN) devices are considered as optimal solutions to meet the requirements of the modern power electronics. In fact, they can allow an improved efficiency in energy conversion at high power, as required today in several strategic application fields (like consumer electronics, renewable energies technology, transportation, electric power distribution, etc.). However, while in the last decades impressive progresses have been recorded both in SiC and GaN devices, the full exploitation of these materials has not been reached yet, due to some open technological key issues. This paper reviews some recent advances in dielectrics technology currently adopted to optimize the performances of SiC and GaN transistors. In particular, in the case of SiC the discussion is focused on the optimization of SiO2/SiC interfaces in 4H-SiC MOSFETs technology by passivation processes of the gate oxides. On the other hand, the current trends in dielectrics passivation for GaN-based HEMTs to limit the gate leakage and the current collapse are discussed. (C) 2014 Elsevier B.V. All rights reserved.