US Patent 11855141 Local epitaxy nanofilms for nanowire stack GAA device

The disclosed technique forms epitaxy layers locally within a trench having angled recesses stacked in the sidewall of the trench. The sizes of the recesses are controlled to control the thickness of the epitaxy layers to be formed within the trench. The recesses are covered by cap layers and exposed one by one sequentially beginning from the lowest recess. The epitaxy layers are formed one by one within the trench with the facet edge portion thereof aligned into the respective recess, which is the recess sequentially exposed for the epitaxy layer.