A metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT) is proposed based on using a Al2O3/ZrO2 stacked layer on conventional AlGaN/GaN HEMT to suppress the gate leakage current, decrease flicker noise, increase high-frequency performance, improve power performance, and enhance the stability after thermal stress or time stress. The MOS-HEMT has a maximum drain current density of 847 mA/mm and peak transconductance of 181 mS/mm. The corresponding subthreshold swing and on/off ratio are 95 mV/dec and 3.3 × 107. The gate leakage current can be reduced by three orders of magnitude due to the Al2O3/ZrO2 stacked layer, which also contributes to the lower flicker noise. The temperature-dependent degradation of drain current density is 26%, which is smaller than the 47% of reference HEMT. The variation of subthreshold characteristics caused by thermal or time stress is smaller than that of the reference case, showing the proposed Al2O3/ZrO2 stacked gate dielectrics are reliable for device applications.