Abstract In this paper, we design and fabricate a Schottky-metal-insulator-semiconductor (MIS) cascode anode GaN lateral field-effect diode (CA-LFED) to achieve ultralow reverse leakage current ( I LEAK ). The device based on AlGaN/GaN high-electron-mobility-transistor (HEMT) includes a normally-off MIS-controlled channel that is cascoded with a high barrier height Schottky contact. At reverse bias, the high electric-field is effectively prevented by the normally-off MIS-controlled channel edge. Together with the high barrier height Schottky contact, this feature significantly suppresses the I LEAK . Supported by the device fabrication, the CA-LFED with high breakdown voltage (BV) > 600 V shows an ultralow I LEAK of 3.6 × 10 −9 A/mm as well as a low forward voltage drop ( V F ) of 2.2 V. The performance suggests that the CA-LFED can be a promising candidate for ultralow I LEAK and better V F - I LEAK trade-off GaN power diode applications.