Capacitance–voltage profiling

The dependence of the depletion width upon the applied voltage provides information on the semiconductor's internal characteristics, such as its doping profile and electrically active defect densities.

These measurements are extremely valuable to product and yield enhancement engineers who are responsible for improving processes and device performance.

Reliability engineers also use these measurements to qualify the suppliers of the materials they use, to monitor process parameters, and to analyze failure mechanisms.

These measurements continue to be important after other process steps have been performed, including lithography, etching, cleaning, dielectric and polysilicon depositions, and metallization, among others.

A metal–oxide–semiconductor structure is critical part of a MOSFET, controlling the height of potential barrier in the channel via the gate oxide.

When a small positive bias voltage is applied to the metal, the valence band edge is driven far from the Fermi level, and holes from the body are driven away from the gate, resulting in a low carrier density, so the capacitance is low (the valley in the middle of the figure to the right).