Semiconductor structure including a varactor

A varactor, comprising:

• a body region comprising an N-doped semiconductor material;
• a gate structure formed over said body region, said gate structure comprising a gate insulation layer and a work function adjustment metal layer over said gate insulation layer;
• wherein said semiconductor material has an electron affinity and a bandgap;
• wherein said work function adjustment metal layer comprises a metal having a work function;
• and
• wherein an absolute value of a difference between said work function of said metal and a sum of said electron affinity and said bandgap of said semiconductor material is smaller than an absolute value of an energy difference between said work function of said metal and said electron affinity of said semiconductor material.

A varactor, comprising:

• a body region comprising a P-doped semiconductor material;
• a gate structure formed over said body region, said gate structure comprising a gate insulation layer and a work function adjustment metal layer over said gate insulation layer;
• wherein said semiconductor material has an electron affinity and a bandgap;
• wherein said work function adjustment metal layer comprises a metal having a work function;
• and
• wherein an absolute value of a difference between said work function of said metal and said electron affinity of said semiconductor material is smaller than an absolute value of a difference between said work function of said metal and a sum of said electron affinity and said bandgap of said semiconductor material.

A device, comprising:

• a body region comprising a silicon germanium layer, wherein said silicon germanium layer in said body region is doped to have a first conductivity type;
• a gate insulation layer over said body region;
• a gate electrode over said gate insulation layer, said gate electrode comprising a conductive work function metal layer over said gate insulation layer and a conductive material formed above said conductive work function metal layer;
• and
• first and second highly doped semiconductor regions adjacent said body region, wherein said first and said second highly doped semiconductor regions are doped to have said first conductivity type and have a higher dopant concentration than said body region, said first and second highly doped semiconductor regions each have a first portion immediately adjacent said gate electrode and a second portion adjacent said first portion and having a first depth greater than a second depth of a lowermost portion of said first portion, and a third depth of said silicon germanium is greater than said second depth, and wherein said body region, said gate insulation layer, said gate electrode, and said first and second highly doped semiconductor regions define a varactor.