[highfreq]

The previous commenter wasn't talking about this transistor 3d feature, but about stacked transistors. Just like a city full or high-rise buildings can pack a lot more people in per square mile, a stacked transistor IC could pack a lot more transistors per square mm.

[jimmywanger]

The only reason we haven't had stacked transistors now is because of trace density/heat dissipation.

We need pin outs and thermal conductivity - stacking layers of transistors is bad for both.