The paper reviews two topics on the non-destructive characterization of high-κ/high-μ gate stacks using hard X-ray(hv=7.94 keV) photoemission spectroscopy. The first topic is the change in the compositional depth profiles and the chemical bonding states of HfO 2/Si-cap/strained-Ge/Si 0.5Ge 0.5/Si(100) laminating structures. The second topic is the influence of HF, (NH 4) 2S and HMDS treatments on In 0.53Ga 0.47As surface, La 2O 3 interlayer insertion on the chemical bonding states at high-κ/In 0.53Ga 0.47As interface. Analyses of Ge 2p, Si 1s and Hf 3d spectra show that the strained-Ge layer is oxidized during the deposition of HfO 2 in the case of 1-nm-thick Si cap layer and that strained-Ge layer is not oxidized in the case of 3 and 5-nm-thick Si cap layer. A critical Si thickness is also extracted. Analyses of measured spectra show that the oxidation of In 0.53Ga 0.47As is suppressed by La 2O 3 interlayer insertion and that (NH 4) 2S treatment can suppress the oxidation of the In 0.53Ga 0.47As surface.