Nothing. Xnm stopped having clear physical meaning when manufacturing moved to non-planar process. TSMC already has 2 nm nodes in research and sub-nm process research is next. sub-1 nm should be coming around 2025.<p>Best way to track progress is to follow MTr/mm² Millions of transistors per square millimeter (it's not exactly transistors but transistors and flip-flops with different weights) It tells us how many logical components tehre are per mm².
It's likely that the nm number will continue to get smaller, since the node name is marketing at this point, and isn't related to any physical semiconductor measurement anymore.<p>As for quantum tunneling, it is likely to be mitigated or exploited at some point. If not, maybe we'll have to use something else, like gallium arsenide[0] instead of silicon.<p>[0] <a href="https://en.wikipedia.org/wiki/Gallium_arsenide" rel="nofollow">https://en.wikipedia.org/wiki/Gallium_arsenide</a>