The number on a process node, 7nm, 5nm, 3nm, is a marketing label, not a measurement of anything physical on the chip. Here is what it actually tracks.
A deep read — the full picture, with the receipts.
When a chipmaker announces a "3nm" processor, the natural assumption is that something on the chip is three nanometers across. That assumption is wrong, and the industry knows it is wrong. The node name is a marketing label. It has not described a real physical dimension for well over a decade.
Understanding why matters, because the node number drives an enormous amount of buying behavior and competitive framing. People compare a "5nm" part from one company against a "4nm" part from another and treat the smaller number as automatically better. The reality is messier and more interesting.
Where the number came from#
In the early decades of chipmaking, the node name really did mean something. It roughly tracked the gate length of a transistor, the physical channel through which current flows when the transistor switches. A 1-micron process had transistors with gate lengths around a micron. As manufacturers shrank that gate length, switching got faster and chips got denser, so the gate length became a convenient shorthand for a whole generation of technology.
That link broke somewhere around the 28nm to 22nm era. Gate lengths stopped shrinking in step with the node name. The physics got in the way: at very small gate lengths, current leaks across the channel even when the transistor is supposed to be off. To keep transistors controllable, engineers changed their shape (the move to FinFET, and later to gate-all-around structures) rather than simply making one dimension smaller.
Discussion