A plasma processing system having a plasma processing chamber configured to process a substrate, comprising: an upper electrode assembly and a lower electrode assembly for processing said substrate, the upper electrode assembly comprising an upper electrode and an upper electrode peripheral extension, the lower electrode assembly comprising a lower electrode and a cover ring, said substrate being disposed on said lower electrode during plasma processing, wherein said upper electrode and said lower electrode are arranged to form a first gap, wherein said upper electrode is arranged such that, in use, it is grounded and wherein said lower electrode is arranged such that, in use, it is powered; wherein said upper electrode peripheral extension is arranged to be mechanically coupled to a periphery of said upper electrode, wherein said upper electrode peripheral extension is configured to be non-coplanar with said upper electrode, wherein said upper electrode peripheral extension is arranged such that, in use, it is grounded, wherein said cover ring is configured to concentrically surround said lower electrode, where said upper electrode peripheral extension and said cover ring are arranged to form a second gap, wherein said second gap is smaller than said first gap, the plasma processing system further comprising a mechanism configured to move one of said upper electrode assembly and said lower electrode assembly in a direction perpendicular to a planar surface of said lower electrode so as to simultaneously adjust said second gap and said first gap and so as to permit differentiated pressure control to provide a wide range of pressure and/or gas conductance in the plasma processing system. an upper electrode assembly and a lower electrode assembly for processing said substrate, the upper electrode assembly comprising an upper electrode and an upper electrode peripheral extension, the lower electrode assembly comprising a lower electrode and a cover ring, said substrate being disposed on said lower electrode during plasma processing, wherein said upper electrode and said lower electrode are arranged to form a first gap, wherein said upper electrode is arranged such that, in use, it is grounded and wherein said lower electrode is arranged such that, in use, it is powered; wherein said upper electrode peripheral extension is arranged to be mechanically coupled to a periphery of said upper electrode, wherein said upper electrode peripheral extension is configured to be non-coplanar with said upper electrode, wherein said upper electrode peripheral extension is arranged such that, in use, it is grounded, wherein said cover ring is configured to concentrically surround said lower electrode, where said upper electrode peripheral extension and said cover ring are arranged to form a second gap, wherein said second gap is smaller than said first gap, the plasma processing system further comprising a mechanism configured to move one of said upper electrode assembly and said lower electrode assembly in a direction perpendicular to a planar surface of said lower electrode so as to simultaneously adjust said second gap and said first gap and so as to permit differentiated pressure control to provide a wide range of pressure and/or gas conductance in the plasma processing system.