The invention provides a method and apparatus for performing plasma etching to form a gate electrode on a large-scale substrate while ensuring the in-plane uniformity of the CD shift of the gate electrode. The present invention measures a radical density distribution of plasma in the processing chamber, feeds processing gases into the processing chamber through multiple locations and controls either the flow rates or compositions of the respective processing gases or the in-plane temperature distribution of a stage on which the substrate is placed, or feeds processing gases into the processing chamber through multiple locations and controls both the flow rates or compositions of the processing gases and the in-plane temperature distribution of the stage on which the substrate is placed.