US Patent 7700453 Method for forming hyper-abrupt junction varactors

Method of fabricating a varactor that includes providing a semiconductor substrate, doping a lower region of the semiconductor substrate with a first dopant at a first energy level, doping a middle region of the semiconductor substrate with a second dopant at a second energy level lower than the first energy level, and doping an upper region of the semiconductor substrate with a third dopant at a third energy level lower than the second energy level.