Semiconductor structure and formation method thereof

A method for forming a semiconductor structure comprising:

• providing a substrate;
• forming a plurality of composite layers on a portion of the substrate, wherein a composite layer of the plurality of composite layers includes a plurality of channel layers stacked one over another and a second gate trench between two neighboring channel layers;
• forming an interlayer dielectric layer on a surface of the substrate and surfaces of the plurality of composite layers;
• forming a first gate trench in the interlayer dielectric layer and a gate sidewall on a side surface of the first gate trench, wherein the first gate trench and the gate sidewall cross over a portion of a sidewall and a portion of a top surface of the composite layer, and the first gate trench communicates with the second gate trench;
• forming a gate in the first gate trench and the second gate trench, the gate and the gate sidewall forming a gate structure;
• forming a doping region in a channel layer under the gate sidewall, a width of the doping region being equal to a width of the gate sidewall along a direction parallel to the substrate;
• and
• forming a source-drain layer in the composite layer on two sides of the gate structure.

A method for forming a semiconductor structure comprising:

• providing a substrate;
• forming a plurality of initial composite layers on a portion of the substrate, wherein an initial composite layer of the plurality of initial composite layers includes a plurality of initial channel layers stacked one over another and a first sacrificial layer between two neighboring initial channel layers;
• forming a dummy gate across the initial composite layer, wherein the dummy gate is formed on a top and a sidewall surface of a portion of the initial composite layer;
• doping a dopant in the initial composite layer exposed by the dummy gate to form an initial doping region in the initial composite layer;
• after forming the initial doping region, forming a gate sidewall on a side surface of the dummy gate to form a dummy gate structure with the dummy gate and the gate sidewall;
• and
• forming a source-drain layer in the initial doping region on two sides of the dummy gate structure, the initial channel layer under the dummy gate structure being used as a channel layer, and the initial doping region in the channel layer being used as a doping region.