The authors proposed a novel alpha-BN/h-BN dual-layered dielectric to fabricate AlGaN/GaN metal-insulatorsemiconductor high electron mobility transistor (MIS-HEMT). In contrast to the Schottky-HEMT, the gate leakage current was suppressed by more than 6 orders of magnitude at forward voltage of 5V. An atomically smooth interface and low interface state density were obtained, benefiting from the quasizero lattice mismatch and the passivation effect of alpha-BN on AlGaN. Electrical analyses demonstrated that boosted gate drive capability, enhanced output current, and high field effect mobility were realized with inserted BN. The electrical breakdown behaviors of BN were investigated with regard to FrenkelPoole emission mechanism and Fowler-Nordheim tunneling theory for the low and high electric field regime, respectively. This work rendered BN as a perfect candidate for dielectric insulator used in fieldeffect transistors. (C) 2020 Elsevier B.V. All rights reserved.