a method of performing a timed etch of a material to a precise depth is provided . in this method , ion implantation of the material is performed before the timed etch . this ion implantation process substantially enhances the etch rate of the material within a precisely controlled depth range corresponding to the range of implantation - induced damage . by using the ion implantation , the variation in vertical etch depth can be reduced by a factor approximately equal to the etch rate of the damaged material divided by the etch rate of the undamaged material . the vertical etch depth can be used to provide a vertical dimension of a non - planar semiconductor device . minimizing vertical device dimension variations on a wafer can reduce device and circuit performance variations , which is highly desirable .