An edge ring assembly is provided, including: an upper edge ring configured to surround an electrostatic chuck (ESC), the ESC having a top surface for supporting a substrate and an annular step surrounding the top surface, the annular step defining an annular shelf that is lower than the top surface, the upper edge ring being disposed above the annular shelf; a lower inner edge ring disposed below the upper edge ring in the annular step and disposed over the annular shelf, the lower inner edge ring being defined from an electrically conductive material, the lower inner edge ring being electrically insulated from the ESC; a lower outer edge ring surrounding the inner edge ring, the lower outer edge ring being disposed below the upper edge ring in the annular step and disposed over the annular shelf, the lower outer edge ring being defined from an electrically insulating material.