Patent ID: 7705428

Claim:
A varactor on a substrate, comprising: a bottom electrode having a plurality of doped regions disposed in the substrate, wherein the doped regions are not arranged regularly in every column and/or row; an upper electrode located over the substrate and comprised of a plurality of openings and a plurality of electrode locations defined by the immediately adjacent openings, wherein each of the electrode locations is surrounded by at least three openings and each of the openings exposes one of the corresponding doped regions, and at least the number of the openings surrounding one of the electrode locations is different from that of the openings surrounding the other electrode location; a first dielectric layer located between the substrate and the upper electrode; and a plurality of conductive lines located over the upper electrode, wherein the conductive lines are parallel strips and physically separate from each other, electrically isolated from the upper electrode, and the conductive lines are electrically connected to the doped regions via the openings.