An electret-based pressure sensitive MOS transistor

The operation of the MOSFET is based on the fact that the lateral conductivity of silicon at the silicon-dioxide-silicon interface strongly depends on the transverse electric field in the oxide. Adding a small air-filled spacer between the metal gate and the oxide, and applying a voltage across the insulator on top of the silicon, the lateral conductivity can become pressure sensitive. The generation of the electric field in the insulator can also be provided by means of an electret. The theory, realization, and performance of an integrated electret-MOSFET-based pressure sensor are presented