A method for processing a workpiece in a plasma reactor chamber having radially inner and outer source power applicators (162, 164) at a ceiling of said chamber facing said workpiece, said inner and outer source power applicators and said workpiece sharing a common axis of symmetry, and a first tilt apparatus adapted to tilt and rotate said outer source power applicator and/or a second tilt apparatus adapted to tilt and rotate said workpiece, said first tilt apparatus and/or second tilt apparatus comprising a ring divided into a pair of rings (200; 360) separated from one another along a slanted plane and comprising a top ring (202; 362) and a bottom ring (204; 364); said method comprising: applying RF source power to said source power applicators (162, 164), and introducing a process gas into the reactor chamber so as to carry out a plasma process on said workpiece characterized by a plasma process parameter, said plasma process parameter having a spatial distribution across the surface of said workpiece; rotating at least one of: (a) said outer RF source power applicator, and (b) said workpiece, about a radial tilt axis for increasing the symmetry of said spatial distribution relative to said common axis of symmetry; reducing the non-uniformity of said spatial distribution by changing said spatial distribution symmetrically with respect to said axis by at least one of: (i) adjusting the ratio of power levels coupled to a plasma process region overlying said workpiece by said inner and outer source power applicators (162, 164); (ii) adjusting the ratio of flow rates of process gases to radially inner and outer regions of said chamber, wherein rotating comprises: rotating the top ring (202; 362) and/or the bottom ring (204; 364) for tilting at least one of: (a) said outer RF source power applicator, and (b) said workpiece, about the radial tilt axis. applying RF source power to said source power applicators (162, 164), and introducing a process gas into the reactor chamber so as to carry out a plasma process on said workpiece characterized by a plasma process parameter, said plasma process parameter having a spatial distribution across the surface of said workpiece; rotating at least one of: (a) said outer RF source power applicator, and (b) said workpiece, about a radial tilt axis for increasing the symmetry of said spatial distribution relative to said common axis of symmetry; reducing the non-uniformity of said spatial distribution by changing said spatial distribution symmetrically with respect to said axis by at least one of: (i) adjusting the ratio of power levels coupled to a plasma process region overlying said workpiece by said inner and outer source power applicators (162, 164); (ii) adjusting the ratio of flow rates of process gases to radially inner and outer regions of said chamber, (i) adjusting the ratio of power levels coupled to a plasma process region overlying said workpiece by said inner and outer source power applicators (162, 164); (ii) adjusting the ratio of flow rates of process gases to radially inner and outer regions of said chamber, wherein rotating comprises: rotating the top ring (202; 362) and/or the bottom ring (204; 364) for tilting at least one of: (a) said outer RF source power applicator, and (b) said workpiece, about the radial tilt axis. rotating the top ring (202; 362) and/or the bottom ring (204; 364) for tilting at least one of: (a) said outer RF source power applicator, and (b) said workpiece, about the radial tilt axis.