Device‐quality thin silicon oxynitride films were successfully prepared by combining remote plasma‐enhanced chemical‐vapor deposition and rapid thermal annealing techniques. The physical, chemical, and electrical properties of the films are determined by the relative flow rates of the N‐atom and O‐atom source gases, NH3and N2O, respectively. Analysis of metal–insulator–semiconductor devices indicated the fixed charges in the dielectric (Qf) and the interface defect state densities (Dit), as determined from the analysis of conventional capacitance–voltage (C–V) measurements, were significantly reduced following post‐deposition rapid thermal annealing. The approximate compositions of the films were obtained by on‐line Auger electron spectroscopy, and the local bonding arrangements were determined by Fourier transform infrared spectroscopy. Correlations between the local bonding structures in the oxynitride films and the electrically active defective states at the Si–SiOyNzinterface are also discussed.