An edge ring assembly used in a plasma etching chamber includes a dielectric coupling ring and a conductive edge ring. In one embodiment, the dielectric coupling ring has an annular projection extending axially upward from its inner periphery. The dielectric coupling ring is adapted to surround a substrate support in a plasma etching chamber. The conductive edge ring is adapted to surround the annular projection of the dielectric coupling ring. A substrate supported on the substrate support overhangs the substrate support and overlies the annular projection of the dielectric coupling ring and a portion of the conductive edge ring. In another embodiment, the dielectric coupling ring has a rectangular cross section. The dielectric coupling ring and the conductive edge ring are adapted to surround a substrate support in a plasma etching chamber. A substrate supported on the substrate support overhangs the substrate support and overlies a portion of the conductive edge ring.