Semiconductor varactor with high capacitance per unit area - has high barrier layer capacitance achieved by means of high doping

摘要

The metal-oxide-silicon semiconductor varactor device has a higher capacitance/unit area, through doping the semiconductor substrate in the region of the varactor, than in the remaining area. The second electrode (SE2) of a transistor (AT) is formed into the same substrate as the varactor. An inversion layer (V) is formed in the surface of the substrate when a potential is applied to the insulated metallisation (LB). The varactor capacitance is a combination of the electrode/inversion layer capacitance and the inversion layer/substrate capacitance (barrier layer capacitance). By increasing the doping of the substrate area below the varactor electrode (SE3), thus reducing the depth of the space-charge zone (RZ), the barrier layer capacitance is increased and with it the total varactor capacitance.