A plasma processing system includes a plasma chamber having a substrate support, and a multi-zone gas injection upper electrode disposed opposite the substrate support. An inner plasma region is defined between the upper electrode and the substrate support. The multi-zone gas injection upper electrode has a plurality of concentric gas injection zones. A confinement structure, which surrounds the inner plasma region, has an upper horizontal wall that interfaces with the outer electrode of the upper electrode. The confinement structure has a lower horizontal wall that interfaces with the substrate support, and includes a perforated confinement ring and a vertical wall that extends from the upper horizontal wall to the lower horizontal wall. The lower surface of the upper horizontal wall, an inner surface of the vertical wall, and an upper surface of the lower horizontal wall define a boundary of an outer plasma region, which surrounds the inner plasma region.