An apparatus for plasma processing a substrate is provided. The apparatus comprises a processing chamber, a substrate support disposed in the processing chamber, a shield member disposed in the processing chamber below the substrate support, and a lid assembly coupled to the processing chamber. The lid assembly comprises a conductive gas distributor coupled to a power source, and an electrode separated from the conductive gas distributor and the chamber body by electrical insulators. The electrode is also coupled to a source of electric power. The substrate support is formed with a stiffness that permits very little departure from parallelism. The shield member thermally shields a substrate transfer opening in the lower portion of the chamber body. A pumping plenum is located below the substrate support processing position, and is spaced apart therefrom.