A method of forming nanosheet and nanowire transistors includes the formation of alternating epitaxial layers of silicon germanium (SiGe) and silicon (Si), where the germanium content within respective layers of the silicon germanium is systemically varied in order to mediate the selective etching of these layers. The germanium content can be controlled such that voids created by removal of the silicon germanium have uniform dimensions, and the backfilling of such voids with gate dielectric and gate conductor layers proximate to silicon nanosheets or nanowires results in devices having a uniform effective gate length.