Silicon nitride (SiNx) films have been prepared at extremely high deposition rates by the atmospheric pressure plasma chemical vapor deposition (AP-PCVD) technique on Si(001) wafers from gas mixtures containing He, H-2, SiH4 and N-2 or NH3. A 150 MHz very high frequency (VHF) power supply was used to generate high-density radicals in the atmospheric pressure plasma. Deposition rate, composition and morphology of the SiNx films prepared with various deposition parameters were studied by scanning electron microscopy and Auger electron spectroscopy. Fourier trans formation infrared (FTIR) absorption spectroscopy was also used to characterize the structure and the chemical bonding configurations of the films. Furthennore, etching rate with buffered hydrofluoric acid (BHF) solution, refractive index and capacitance-voltage (C-V) characteristics were measured to evaluate the dielectric properties of the films. It was found that effective passivation of dangling bonds and elimination of excessive hydrogen atoms at the film-growing surface seemed to be the most important factor to form SiNx film with a dense Si-N network. The C-V curve of the optimized film showed good interface properties, although further improvement was necessary for use in the industrial metal-insulator semiconductor (MIS) applications. (c) 2004 Elsevier B.V. All rights reserved.