High breakdown enhancement mode gallium nitride (GaN) based high electron mobility transistors (HEMTs) with integrated slant field plates. These HEMTs have an epilayer structure comprised of AlGaN/GaN buffer. Before the formation of the gate electrode, a passivation layer is deposited, and then the opening for the gate is patterned. The passivation layer below the gate is etched using an etch condition that creates a slanted sidewalls. Then, the charge below the channel is removed either by Fluorine-based plasma treatment and/or by a recess etch. The gate metal is deposited with an angled rotation to form a gate structure with an inherent field plate with rounded edges.