The charge neutrality level of SiO2 is experimentally extracted by investigating conduction band offset (CBO) of SiO2/Si stack with different SiO2 thicknesses using X-ray photoelectron spectroscopy. The CBO is found to be dependent on SiO2 thickness. The CNL of SiO2 is determined to be 4eV above valence band maximum by modeling the CBO vs. thickness of SiO2 using gap states and charge neutrality level based model. (C) 2017 Elsevier B.V. All rights reserved.