A plasma reactor includes a chamber body having an interior space that provides a plasma chamber and having a ceiling, a gas distributor to deliver a processing gas to the plasma chamber, a pump coupled to the plasma chamber to evacuate the chamber, a workpiece support to hold a workpiece facing the ceiling, an intra-chamber electrode assembly that includes an insulating frame and a filament extending laterally through the plasma chamber between the ceiling and the workpiece support, the filament including a conductor at least partially surrounded by an insulating shell that extends from the insulating frame, and a first RF power source to supply a first RF power to the conductor of the intra-chamber electrode assembly.