The paper reports a normally-off n-channel AlGaN/GaN hybrid metal-oxide-semiconductor heterojunction field-effect transistor (MOS-HFET) on Si substrate with high field-effect mobility. To decrease the channel resistance and to improve the field-effect mobility, of the MOS-HFET, a selective area growth (SAG) technique is applied at the channel region. The fabricated MOS-HFET exhibits a good normally-off operation with the threshold voltage of 3.7 V. the specific ON-state resistance of 7.6 m Omega cm(2), and the breakdown voltage of over 800 V. (C) 2010 Elsevier Ltd. All rights reserved.