A plasma processing chamber for depositing a film on an underside surface of a wafer, includes showerhead pedestal. The showerhead pedestal includes a first zone and a second zone. An upper separator fin is disposed over a top surface of the showerhead pedestal and a lower separator fin is disposed under the top surface of the showerhead pedestal and aligned with the upper separator fin. The first zone is configured for depositing a first film to the underside surface of the wafer and the second zone is configured for depositing a second film to the underside surface of the wafer. In another embodiment, a top surface of the showerhead pedestal may be configured to receive a masking plate instead of the upper separator fin. The masking plate is configured with a first area that has openings and a second area that is masked. The first areas is used to provide the process gas to a portion of the underside surface of the wafer for depositing a film.