LPCVD-silicon oxynitride films with different compositions were deposited on n-Si(111) substrates by reacting dichlorosilane (SiH 2 Cl 2 ) with nitrous oxide (N 2 O) and ammonia (NH 3 ) at a temperature of 860 o C varying the gas flow rate ratio of N 2 O and NH 3 . The electrical properties of the SiO x N y films were studied by analysis of the 1 MHz capacitance-voltage characteristics of the metal-SiO x N y -silicon capacitors. It has been found that with increasing amount of N 2 O in the deposition ambient the concentration of the dielectric charges in the SiO x N y /Si structures goes through a minimum, while the interface trap density gradually decreases. The nature of the defects is discussed.