SEMICONDUCTOR STRUCTURE AND FORMATION METHOD THEREOF

A semiconductor structure includes a plurality of composite layers formed on a portion of a substrate. An interlayer dielectric layer is formed on the substrate and the plurality of composite layers. A first gate trench is formed on the interlayer dielectric layer, and a gate sidewall is formed on a side surface of the first gate trench. The composite layer includes stacked channel layers and a second gate trench between neighboring channel layers. 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. A gate is formed in the first and second gate trenches. The doping region is formed in a channel layer. The source-drain layer is formed in the composite layer on two sides of the gate structure.