Illustration: Bryan Christie Design

RUNNING OUT OF ATOMS: The transistor’s gate oxide thinned with each new technology generation until it reached just 5 atoms (1.2 nm) thick. At that scale, the wave describing the probable location of an electron [red curve, top] is broader than the gate oxide, and the electron can simply appear on the other side of the gate oxide, having tunneled through the insulation. This so-called gate ­leakage increased 100-fold in the last three generations of transistors. A switch to a new gate oxide, a high-k dielectric, was needed to plug the leak.