US Patent 12107168 Independent gate length tunability for stacked transistors

A stacked FET structure having independently tuned gate lengths is provided to maximize the benefit of each FET within the stacked FET structure. Notably, a vertically stacked FET structure is provided in which a bottom FET has a different gate length than a top FET. In some embodiments, a dielectric spacer can be present laterally adjacent to the bottom FET and the top FET. In such an embodiment, the dielectric spacer can have a first portion that is located laterally adjacent to the bottom FET that has a different thickness than a second portion of the dielectric spacer that is located laterally adjacent the top FET.