Wide band gap (WGB) materials are the most promising semiconductors for future electronic devices, and are candidates to replace the conventional materials (Si, GaAs, …) that are approaching their physical limits. Among WBG materials, silicon carbide (SiC) and gallium nitride (GaN) have achieved the largest advancements with respect to their material quality and device processing. Clearly, the devices performances depend on several surface and interface properties, which in turn are often crucially determined by the quality of the available material, as well as by the device processing maturity. In this paper, some surface and interface issues related to SiC and GaN devices processing are reviewed. First, the control of metal/SiC barrier uniformity and surface preparation will be discussed with respect to the performance of Schottky-based devices. Moreover, the impact of high-temperature annealing required for …