Semiconductor structure and forming method thereof

A method for forming a semiconductor structure comprises the steps that a substrate is provided, the substrate comprises a substrate body and a fin part protruding on the substrate body, the fin part comprises a channel region in the extending direction of the fin part, and the channel region is used for forming a laminated work function layer; forming a gate dielectric layer covering the top and the side wall of the fin part in a shape-preserving manner in the channel region; forming a first work function layer covering the gate dielectric layer in a conformal manner in the channel region; a filling layer is formed on the first work function layer between the adjacent fin parts, the filling layer at least exposes the first work function layer at the tops of the fin parts, and the material Fermi level of the filling layer is closer to the Fermi level of the fin parts compared with the material Fermi level of the laminated work function layer; and forming a second work function layer covering the first work fu