A toroidal plasma source (28) within a substrate processing chamber (10). The toroidal plasma source forms a poloidal plasma with theta symmetry. The poloidal plasma current is essentially parallel to a surface of the plasma generating structure, thus reducing sputtering erosion of the inner walls. The plasma current is similarly essentially parallel to a process surface (32) of a substrate (34) within the chamber. In a further embodiment, a shaped member (66) between the substrate and the plasma source controls the plasma density in a selected fashion to enhance plasma processing uniformity.