In previous studies, device-quality Si-SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process: (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (similar to0.6 nm) and (ii) remote plasma-enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to the GaN-SiO2 system. Without an RPAO step, subcutaneous oxidation of GaN takes place during RPECVD deposition of SiO2, and on-line Auger electron spectroscopy indicates a similar to0.7-nm subcutaneous oxide. The quality of the interface and dielectric layer with/without RPAO process has been investigated by fabricated GaN metal-oxide-semiconductor capacitors. Compared to single-step SiO2, deposition, significantly reduced defect state densities are obtained at the GaN-SiO2, interface by independent control of GaN-GaOx, interface formation by RPAO and SiO2, deposition by RPECVD. (C) 2004 American Vacuum Society.