[adrian_b]

There are no features with lengths of 3 nm, 7 nm etc.

Some vertical distances, e.g. thicknesses, are indeed of only a few nm, but the process size name always referred strictly to horizontal distances (i.e. parallel with the wafer surface), which are determined by lithography. Those are at least 10 times larger, in the range 25 nm to 60 nm for modern processes.

There are a few horizontal distances that are not determined by lithography, i.e. they do not correspond with something drawn on the mask, but the distances are determined by speeds of corrosion or diffusion, like also for the vertical dimensions, but those also do not count for naming processes, because you could have such a distance of only e.g. 5 nm even in an 180 nm process. Those distances that are not determined by lithography do not influence the potential density of a circuit but only certain electrical performances.