EOT (equivalent oxide thickness): definition

Beginner

How thin the insulating layer under the gate effectively is. Thinner gives the gate a stronger grip.

Novice

The thickness of plain silicon dioxide that would give the same gate capacitance as the real gate insulator. High-k insulators let the physical layer stay thicker (less leakage) while the EOT keeps shrinking.

Expert

$t_{\mathrm{phys}} \cdot \varepsilon_{\mathrm{SiO_2}} / \varepsilon_{\text{high-}k}$ plus interfacial layer. It sets $C_{\mathrm{ox}}$ , so it enters both the body factor and $\lambda$ . Around 1 nm in modern high-k/metal-gate stacks; going lower raises gate tunneling and mobility loss, which is part of why architecture ( $N$ ) took over as the scaling knob.