The valence band electronic structure of silicon nitride (Si3N4) is studied using the first principal quantum chemical calculation, X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Assuming that the valence band is formed with N 2p and Si 3s, 3p and 3d electrons and based on the XPS and UPS results, the valance band offset at the Si/Si3N4 interface was estimated to be 1.5+/-0.2 eV. This hole barrier explains the hole dominating conduction in Si/Si3N4 structure when a positive potential is applied to the silicon substrate. In addition, the UPS study reveals that the valence band offset at the Si3N4/silicon oxide inter-face is 2.5+/-0.2 eV, (C) 2003 Elsevier Science B.V. All rights reserved.