Techniques are disclosed for non-planar transistors having varying channel widths (Wsi). In some instances, the resulting structure has a fin (or nanowires, nanoribbons, or nanosheets) comprising a first channel region and a second channel region, with a source or drain region between the first channel region and the second channel region. The widths of the respective channel regions are independent of each other, e.g., a first width of the first channel region is different from a second width of the second channel region. The variation in width of a given fin structure may vary in a symmetric fashion or an asymmetric fashion. In an embodiment, a spacer-based forming approach is utilized that allows for abrupt changes in width along a given fin. Sub-resolution fin dimensions are achievable as well.