Si 2p and N 1s spectra arising from a oxynitride film formed on Si(1 0 0) surface were measured in the photon energy range from 556 to 1471 eV, where the electron escape depth in SiO2 changes from 1.68 to 3.80 nm. It was found for the first time that the photon energy dependence of N 1 s and Si 2p photoelectron spectra can be nearly reproduced if the depth profile of nitrogen atoms is known. (C) 2003 Elsevier Science B.V. All rights reserved.