We have investigated the effect of La2O3 interlayer insertion on the thermal stability of a high-κ/In0:53Ga 0:47 As interface and the chemical bonding states at the high-κ/In0:53Ga0:47As interface by hard X-ray (hv = 7:94keV) photoemission spectroscopy (HX-PES). The control of the oxide formation at the HfO2/In0:53Ga0:47As interface was tried by inserting La2O3, which has a large Gibbs free energy. Analyses of As 2p, Ga 2p, In 3d, Hf 3d, La 3d, and W 4f spectra show that the oxidation of In0:53Ga0:47As was suppressed by La 2O3 interlayer insertion. We have also investigated the effect of surface treatment on the chemical bonding state of the In 0:53Ga0:47As surface. (NH4)2S treatment can suppress the oxidation of the In0:53Ga0:47As surface.