Methods and apparatus for processing substrates are disclosed herein. In some embodiments, a substrate support to support a substrate in a processing chamber includes a dielectric insulator plate; a conductive plate supported on the dielectric insulator plate, the conductive plate comprising a top surface and a bottom surface defining a thickness between the top surface and the bottom surface, wherein an edge portion of the conductive plate tapers in a radially outward direction; and a dielectric plate comprising a substrate support surface disposed upon the top surface of the conductor plate.