For the interfaces of CVD Si3N4 on Si(1 0 0) and directly-nitrided Si(I 0 0), chemical bonding features, energy band offsets and defect state density distributions have been studied using high-resolution X-ray photoelectron spectroscopy and total photoelectron yield spectroscopy. At nitride-Si(I 0 0) interfaces, Si-N bonding states in which each Si atom is bonded with one or three N atoms are formed predominantly, being presumably related to the structural strain induced by Si-N bonding at the interface. For nearly stoichiometric SiNx (x greater than or equal to 1.3) in the thickness range of 1.0-17 nm which was prepared by 750 degreesC CVD or 700 degreesC direct-nitridation, the energy band gap was determined to be 5.4 +/- 0.1 eV from the energy loss spectra of N Is photoelectrons. By analyzing the valence band spectra of thin SiNx/Si(1 0 0) heterostructures, the valence band offset between such SiNx and Si(1 0 0) was obtained to be 1.9 +/- 0.1 eV. For the direct-nitridation of Si(1 0 0) at 600 or 700 degreesC, an interface state density as low as similar to 10(10) eV(-1) cm(-2) near Si midgap was confirmed by total photoelectron yield measurements. (C) 2003 Elsevier Science B.V. All rights reserved.