AN2386

MOS structure

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1

MOS structure

As it is well known, a MOS structure is composed by three layers: the first one is metal or

one is the semiconductor (see Figure 1.).

Figure 1.

Cross section view of a MOS capacitor

Considering an ideal MOS system with a p-doped semiconductor, the energy band diagram

can be illustrated as in Figure 2.

Figure 2.

Energy band diagram of an ideal MOS capacitor under thermal

equilibrium.

q

the energy difference between the oxide conduction band and the metal Fermi energy level

(metal-to-oxide barrier energy); q

energy difference between the vacuum level and the conduction band edge.

from the semiconductor to the metal, the vacuum level must bend up gradually to