Chipmakers are running out of room for ordinary transistors

When a transistor is only dozens of atoms wide

A chip’s “feature size” describes tiny structures made during manufacturing; it does not mean every part of a transistor has that exact width. But some important transistor dimensions are now measured in just a few dozen silicon atoms. At that scale, a change of only a few atoms can noticeably alter a component’s behavior.

That matters because a transistor is a controllable switch. In a familiar design, a gate acts like a valve: applying voltage lets current flow through a channel, and removing it should shut the current off. Shrinking the channel helps pack more switches onto a chip, but the insulating barriers and other critical layers shrink too.

Why atoms make scaling harder

At ordinary scales, engineers can treat materials as continuous and predictable. Near atomic dimensions, the arrangement of individual atoms matters. A tiny variation in a barrier’s thickness can change how well it blocks current. And electrons can sometimes tunnel through a barrier—crossing it even when classical physics says they should not. The result can be leakage: current flowing through a transistor that is supposed to be off, wasting power and producing heat.

Manufacturing also becomes less forgiving. A slight irregularity that would be negligible in a larger structure can make neighboring transistors behave differently, complicating efforts to produce reliable chips in enormous numbers.

Progress shifts from shrinking alone

The response is not simply to stop improving chips. Engineers have changed transistor shapes and arrangements, including designs that surround the channel with the gate more completely, and they continue to refine materials and chip architecture. These approaches can improve control or performance without relying only on making every feature narrower.

The practical limit is therefore not a single line where transistors suddenly stop working. It is a growing tradeoff: shrinking can add capability, but atomic-scale leakage, variation, power use, and manufacturing difficulty make each further step harder.