A substrate support utilized in high-density plasma chemical vapor deposition (HDP-CVD) processing functions as a radio frequency (RF) electrode (e.g., a bias RF cathode). An upper surface of the substrate support has a central upper surface portion and a peripheral upper surface portion, with the peripheral upper surface portion recessed relative to the central upper surface portion. The upper surface of the support extends beyond an outer edge of the substrate when the substrate is positioned on the substrate support. This extension in the support upper surface may enhance process performance by reducing electric field edge effects, as well as by improving directional distribution of ions traveling to the substrate. Since the peripheral upper surface portion is recessed relative to the central upper surface portion, a detachable shield can be disposed on the peripheral upper surface portion for preventing undesirable deposition on, or chemical attack of, the peripheral upper surface portion, without interfering with positioning of the substrate.