[londons_explore]

Todays transistors are still generally on a plane. If we could find ways to build IC's stacked thousands or millions of layers thick, we could really start using the third dimension.

("3d" transistors built on their side don't really count)

[CodesInChaos]

For CPUs/GPUs it probably wouldn't help that much, since you have to get rid of the heat produced by switching a transistor.

And for storage the main issue isn't how big it is, but how cheap it is to manufacture.