This article proposed a new extended gate towards a source in AlGaN/GaN metal-oxide-semiconductor-high-electron-mobility transistors in order to increase breakdown voltage and reduce on-resistance. The TaN gate was isolated from the source by a 15 nm-thick RF-sputtered HfO sub( 2) gate insulator. A high breakdown voltage of 1410 V was measured as a result of the successfully blocked gate leakage current and surface passivation by the HfO sub( 2) gate insulator. The extended gate towards the source was an effective method to improve the on-resistance and drain current density by eliminating the gate-source space. The proposed device with the extended gate exhibited low specific on-resistance of 2.28 m Omega ...cm super( 2) while that of the MOS-HEMT with the conventional structure was 2.91 m Omega ...cm super( 2). Also, maximum drain current density at the V sub( GS) of 2 V was increased from 332 to 420 mA/mm by the proposed extended TaN gate.(ProQuest: ... denotes formulae/symbols omitted.)