Effect of W and TiN/W gate metal on the interface quality of La2O3/InGaAs metal-oxide-semiconductor (MOS) interface is investigated. Hard X-ray photoelectron spectroscopy revealed that gate metal greatly affects the oxidation states at La2O3/InGaAs interface after post-metallization annealing (PMA). Results demonstrate that TiN/W gate metal can effectively control the reaction at La2O3/InGaAs interface and also suppress the formation of As, Ga, and In oxides. As a result, superior capacitance-voltage (C-V) characteristics with low interface state density (D-it) of 4.6 x 10(11) cm(-2)/eV (similar to 0.1 eV from midgap) and leakage current below 10(-5) A/cm(2) was obtained for TiN/W/La2O3 (10 nm)/InGaAs MOS capacitors. The MOS structure integrity was preserved for annealing temperature up to 620 degrees C. (C) 2013 Elsevier Ltd. All rights reserved.