A method of oxidizing a substrate having area of about 30,000 mm2 or more. The surface is preferably comprised of silicon-containing materials, such as silicon, silicon germanium, silicon carbide, silicon nitride, and metal suicides. A mixture of oxygen-bearing gas and diluent gas normally non-reactive to oxygen, such as Ne, Ar, Kr, Xe, and/or Rn are ionized to create a plasma having an electron density of at least about 1e12 cm−3 and containing ambient electrons having an average temperature greater than about 1 eV. The substrate surface is oxidized with energetic particles, comprising primarily atomic oxygen, created in the plasma to form an oxide film of substantially uniform thickness. The oxidation of the substrate takes place at a temperature below about 700° C., e.g., between about room temperature, 20° C., and about 500° C.