Counter-doped varactor structure and method

A method for forming a varactor diode, comprising:

• providing a substrate having a first surface, then in any order;
• forming a first region of a first conductivity type and first peak dopant concentration in or on the substrate proximate the first surface;
• providing a second region of a second, opposite conductivity type and second peak dopant concentration in the substrate located beneath the first region;
• forming a third region of the second conductivity type and third peak dopant concentration located in the substrate beneath the second region;
• and
• providing a fourth counter-doped region of the first conductivity type and fourth peak dopant concentration located at a depth between a depth of the peak concentration of the second region and a depth of the peak concentration of the third region, thereby forming a P+NPN or N+PNP structure for the varactor diode.

A varactor diode, comprising:

• a substrate having a first surface;
• a P+ region in or on the substrate proximate the first surface;
• a first N region in the substrate located beneath the P+ region;
• an N well region located in the substrate beneath the first N region;
• and
• a first P type counter-doped region located between the first N region and the N well region, thereby forming a P+NPN structure for the varactor diode.