Correction: it’s not stacking. They do things like FinFET (turning the gates in the third dimension) and gate-all-around which increases the density of transist

Correction: it’s not stacking. They do things like FinFET (turning the gates in the third dimension) and gate-all-around which increases the density of transistors per unit area. But they don’t have layers of transistors. At least in the logic and analog processes.