US Patent 11177369 Stacked vertical field effect transistor with self-aligned junctions

A method of forming a semiconductor device and resulting structure in which a trench is formed extending through a plurality of layers on a semiconductor substrate. The plurality of layers includes a sequence of dielectric materials. A first portion of the plurality of layers corresponds to a bottom vertical field effect transistor (VFET) and a second portion of the plurality of layers corresponds to a top VFET. A sacrificial layer separates the bottom VFET from the top VFET. A fin is formed within the trench by epitaxially growing a semiconductor material. A hard mask is formed above a central portion of the plurality of layers. Portions of the plurality of layers not covered by the hard mask are removed. The first portion of the plurality of layers is covered to remove the sacrificial layer. The recess resulting from the removal of the sacrificial layer is filled with an oxide material.