In a stacked-transistor architecture, interconnections must run vertically between transistors rather than only at the top or bottom.

“But the act of stacking does not mean that they're not interconnected. What used to be connections on the top or even on the bottom, as you've seen from our press release, now has to go vertically in between the transistors, and that's a new challenge, because the aspect ratio of creating trenches and filling those trenches becomes more and more difficult.”