Silicon carbide (SiC) and gallium nitride (GaN) are excellent wide band gap materials for power electronics. In spite of the significant progresses achieved in the last years, there are several issues limiting the performances of the developed devices. As an example, interfaces in SiC and GaN-based structures represent still one of the major concerns. Among them, metal/p-type SiC (or GaN) interfaces and metal-oxide-semiconductor (MOS) interfaces are fundamental building blocks for the performances of both diodes and transistors. In this context, the improvement of the related technology requires further efforts to better understand some physical aspects related to these interfaces. This paper reviews some of our recent results related to metal/semiconductor (ohmic contacts) and metal-oxide-semiconductor interfaces to p-type SiC and GaN. Firstly, the impact of the morphology of p-type implanted SiC, annealed under different conditions, on the properties of Ti/Al contacts will be discussed. The influence of different annealing conditions on the channel mobility in 4H-SiC MOSFETs will be also addressed. In the second part of the paper, the evolution of microstructure and Schottky barrier height in Ni/Au contacts to p-type GaN will be presented. All these aspects will be discussed in the present context of SiC and GaN research, considering the practical implications for devices. (c) 2012 Elsevier B.V. All rights reserved.