Normally-off AlGaN/GaN-based MOS-HEMT has been fabricated by utilizing damage-free self-terminating tetramethyl ammonium hydroxide (TMAH) recess etching. The device exhibited a threshold voltage of +2.0 V with good uniformity, extremely small hysteresis of similar to 20 mV, and maximum drain current of 210 mA/mm. The device also exhibited excellent off-state performances, such as breakdown voltage of similar to 800 V with off-state leakage current as low as similar to 10(-12) A and high on/off current ratio (I-on/I-off ) of 10(10). These excellent device performances are believed to be due to the high quality recessed surface, provided by the simple self-terminating TMAH etching.