Patent ID: 7714412

Claim:
A varactor structure comprising: a semiconductor substrate including a subcollector of a second conductivity type located below an upper region of said semiconductor substrate and a semiconductor layer of a first conductivity type beneath the subcollector, said first conductivity type is different from said second conductivity; a well region located in said upper region of said semiconductor substrate, wherein said well region includes outer well regions of said second conductivity type and an inner well region of said first conductivity type, each well of alternating conductivity type of said well region is separated at an upper surface by an isolation region, wherein the outer well region and the inner well region each have an upper surface that includes source and drain dopant regions, wherein the source and drain dopant regions of the inner well regions are separated from the source and drain dopant regions of the outer well regions by the isolation region comprising a dielectric material; and a field effect transistor having at least a gate conductor of said first conductivity type located above said inner well region, the outer well regions and the inner well region are in contact with the subcollector having the second conductivity type, wherein said each well of alternating conductivity type of said well region extends beneath the isolation region to the subcollector such that neighboring well regions are in contact with each other along an entire depth of each well region, wherein the subcollector continuously extends through the outer well region and the inner well region of the semiconductor substrate.