A high-performance normally off recess-gated aluminium gallium nitride (AlGaN)/GaN metal–insulator–semiconductor field-effect transistor (MISFET) is successfully demonstrated with operation temperature of 200°C which was fabricated by using a self-terminating gate recess etching technique. At 200°C, by employing a high-quality aluminium oxide/silicon nitride bilayer as gate dielectrics, the fabricated device exhibits a high threshold voltage of 4.5 V, a high drain current density of 321 mA/mm, a low off-state leakage current of 20 μA/mm as well as a high on/off current ratio of ∼10⁶. Furthermore, a high forward gate breakdown voltage of 23.6 V (∼7.9 MV/cm) and an off-state breakdown voltage as high as 1055 V are obtained in the fabricated device, both of which, as far as it is known, is the highest reported value in normally off GaN devices operated at 200°C. The high threshold voltage, large drain current density, low off-state leakage current, high gate breakdown voltage as well as high off-state breakdown voltage make this normally off recess-gated AlGaN/GaN MISFET very suitable for high-temperature power switch applications.