Short-channel effects: definition

Beginner

Problems a transistor gets when it’s so short that the far end, the drain, starts to fight the gate. It leaks and doesn’t switch off cleanly.

Novice

The set of ways a transistor misbehaves once its gate is too short for the gate to dominate the channel: the drain voltage lowers the threshold (DIBL), the turn-off gets less steep (worse subthreshold swing), and the threshold falls as the gate gets shorter (roll-off).

Expert

2D electrostatic effects that appear when $L$ is only a few natural lengths $\lambda$ : $V_{\mathrm{T}}$ roll-off, DIBL, degraded SS and, in the limit, punch-through. They grow roughly as $\exp(-L/2\lambda)$ , so the fix is to shrink $\lambda$ (thinner channel, thinner EOT, more gates) rather than only $L$ .