There are various areas. 3DNAND is a fully 3D design, and scaled reasonably past the limits of 2D. Crosspoint memory is a simplified 3D structure. In logic, pe

There are various areas. 3DNAND is a fully 3D design, and scaled reasonably past the limits of 2D. Crosspoint memory is a simplified 3D structure. In logic, people (Unity, for instance) talk about fully 3D, with stacks of transistors layered. This turns out to be capability and thermally limited. The most interesting variant today are the N over P nanosheets. Instead of having N and P transistors next to each other, putting them on top saves area. Contact and interconnect are still limiting, but this gives a node shrink without lateral shrink. It isn't completely obvious to me that this gives enough design flexibility to be worth it, but maybe? So anyway, there are good attempts, and the stacked NPN is the most likely.