MOSFET

If only the thickness of the gate insulator is reduced, without changing its material or area, what happens to the gate capacitance per unit area?

  1. AIt increases
  2. BIt decreases
  3. CIt does not change
Show answer and explanation

Answer: A. It increases

The gate can be treated as a parallel-plate capacitor, C = ε / t (ε: permittivity, t: thickness). Thinning the film increases the capacitance and strengthens the gate's control over the channel. However, if it is made too thin, gate leakage due to tunneling increases, which is why high-k materials with higher permittivity came into use.

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