We report the fabrication of AlGaN/GaN high electron mobility transistor (HEMT) with high breakdown voltage by employing the metal-insulator-semiconductor (MIS) gate structure. SiO2, SiN, and TiO2 were used for the insulators. The gate leak current was significantly reduced by employing the MIS structure, and the breakdown voltage characteristics were improved. The breakdown voltage of the MIS-HEMTs increased non-linearly with the increase of gate-drain length L-gd. The TiO2 insulator exhibited highest breakdown voltage of 2 kV with the on-resistance of 15.6 m Omega cm(2) for L-gd = 28 mu m. On the other hand, the breakdown voltage and on-resistance for SiN MIS-HEMT were found to be 1.7 kV and 6.9 m Omega cm(2), respectively. We demonstrated that AlGaN/GaN MIS-HEMTs are promising not only for high speed applications but also for high power switching applications. (c) 2006 Elsevier Ltd. All rights reserved.