High-performance enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor HEMTs (MISHEMTs) were realized by using fluorinated Al2O3 thin films as gate dielectrics. The depth profile of Fluoride atoms determined by X-ray photoelectron spectroscopy showed that the fluorine (F) ions were incorporated into the surface (approximately 2 nm) of the Al2O3 gate dielectrics. With proper amount of F-ion incorporation, the threshold voltage of MISHEMTs shifted from - 4.8 to 0.11 V, converting depletion-mode (D-mode) MISHEMTs to E-mode ones. The E-mode MISHEMTs exhibited high performances including a high transconductance value of 153 mS/mm and a large saturated drain-current value Ids of 547 mA/mm. This paves a new way to fabricate E-mode AlGaN/GaN MISHEMTs and allows the monolithic integration of E/D-mode MISHEMTs for analog integrated circuits.