Silicon oxynitride films were deposited on Si by plasma-enhanced chemical vapor deposition using ammonia, nitrous oxide, and silane as precursors and subjected to preannealing in an oxygen atmosphere at 1100 or 1150 degrees C under atmospheric pressure (10(5) Pa) for 5 h. The oxynitride films were then further processed at temperature up to 1100 degrees C under argon hydrostatic pressure up to 1.2 GPa. The effects of high temperature-high hydrostatic pressure (HT-HP) treatment on the surface morphology, chemical bonding, crystallization effect, and photoluminescence (PL) of the SiON films were investigated. The PL intensity of silicon-rich oxynitride films is significantly enhanced by HT-HP processing. An explanation of this effect has been suggested. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3543650] All rights reserved.