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Aluminum-based high-permittivity (high-k) gate dielectrics and suitable metal electrodes were systematically designed for advanced SiC power metal-oxide-semiconductor field-effect transistors (MOSFETs). Although electron injection into alumina (Al2O3) was significantly suppressed by nitrogen incorporation (aluminum oxynitride: AlON), gate leakage current under negative gate bias and hole trapping into the dielectrics were observed. Adding hafnium into the AlON (HfAlON) was investigated to overcome these drawbacks, and an atomic layer deposition-based method for HfAlON was developed in terms of permittivity, energy bandgap, and hole conduction under negative stressing conditions. Consequently, the reliability of metal/high-k gate stacks under both positive and negative bias temperature stresses was improved by using an optimized HfAlON gate dielectric in combination with a high work-function TiN gate electrode. Thanks to the higher permittivity of HfAlON, peak transconductance was successfully enhanced up to 3.4 times with an acceptable reliability margin in the state-of-the-art trench SiC MOSFETs by implementing a TiN/HfAlON gate stack.