We report a new fabrication process to realize a slant field plate - a field plate in which the plate-to-channel distance gradually increases with the distance from the gate edge - using a multi-layer SiCN film. AlGaN/GaN HEMTs with several types of field plates are fabricated by this technique. The current collapse in the pulsed measurements is suppressed by the slant field plates more effectively than the conventional parallel-plate field plates as a result of the reduced electric field at the gate edge. (C) 2014 Elsevier Ltd. All rights reserved.