Semiconductor Structure and Manufacturing Method Thereof

A method comprising:

• forming a gate structure in an epitaxial layer that is disposed on a substrate, the gate structure extending from a top surface of the epitaxial layer into the epitaxial layer;
• forming a first lightly doped layer in the epitaxial layer, the first lightly doped layer extending from the top surface of the epitaxial layer toward the substrate;
• forming a heavily doped layer in the first lightly doped layer;
• forming a second lightly doped layer in the first lightly doped layer;
• and
• forming a portion of the second lightly doped layer into a first portion of a metal silicide layer, a top surface of the metal silicide layer being coplanar with a top surface of the gate structure;
• and
• wherein before forming the portion of the second lightly doped layer into the first portion of the metal silicide layer, a doping concentration of the portion of the second lightly doped layer is less than a doping concentration of the heavily doped layer.

A semiconductor structure comprising:

• an epitaxial layer on a substrate;
• a first lightly doped layer on the epitaxial layer;
• a second lightly doped layer on the first lightly doped layer;
• a heavily doped layer on the first lightly doped layer, the second lightly doped layer adjoining the heavily doped layer, a top surface of the heavily doped layer being coplanar with a top surface of the second lightly doped layer, and the heavily doped layer having a thickness greater than the second lightly doped layer;
• a metal silicide layer on the second lightly doped layer and the heavily doped layer;
• and
• a gate structure, extending from a top surface of the metal silicide layer toward the substrate and into the epitaxial layer, the gate structure comprising:
• an electrode layer;
• an isolation layer, disposed on the electrode layer;
• and
• a dielectric oxide layer surrounding the electrode layer and the isolation layer, wherein a top surface of the isolation layer and a top surface of the dielectric oxide layer are coplanar with the top surface of the metal silicide layer;
• and
• wherein a doping concentration of the second lightly doped layer at an interface between the second lightly doped layer and the metal silicide layer is less than a doping concentration of the heavily doped layer.