In this work, we report the investigation of the band alignment of SiO2/(AlxGa1-x)(2)O-3 (0 <= x <= 0.49) utilizing the high resolution X-ray photoelectron spectroscopy (XPS) measurements. The single crystallinity and orientation of beta-(AlxGa1-x)(2)O-3 films grown on sapphire by pulsed laser deposition were studied with the high resolution X-ray diffraction. The Ga2p(3/2) and Si 2p core-level spectra as well as valence band spectra were used in the analysis of band alignment. As the mole fraction x of Al increases from 0 to 0.49, the bandgap and conduction band offset values of SiO2/(AlxGa1-x)(2)O-3 increases from 4.9 to 5.6 eV and from 1.5 to 2.1 eV, respectively, while that of valence band offset decreases from 2.2 to 0.9 eV. From the results obtained, the energy band diagram of the studied SiO2/(AlxGa1-x)(2)O-3 (0 <= x <= 0.49) interfaces is found to be of type I. Energy band lineups of SiO2/(AlxGa1-x)(2)O-3 were thus determined which can be used as for Ga2O3 based power device technology. (C) 2017 Elsevier B.V. All rights reserved.