Semiconductor structure and formation method thereof

Abstract

A semiconductor structure and a formation method thereof are disclosed. The formation method includes: providing a base, wherein a first mandrel layer and a first mask layer located on the first mandrel layer are formed on the base, and openings exposing the first mandrel layer are formed in the first mask layer; forming a second mandrel layer covering the first mask layer, wherein the second mandrel layer also fills the openings; forming first trenches running through the second mandrel layer, the first mask layer and the first mandrel layer, wherein the side walls of the first trenches expose the second mandrel layer in the openings; forming side wall layers on the side walls of the first trenches; and etching to remove the second mandrel layer and the first mandrel layer below the positions of the openings by taking the side wall layers as masks to form second trenches running through the first mandrel layer, wherein the second trenches and the first trenches are isolated by the side wall layers. The present disclosure enlarges a process window for forming the second trenches under the protective effect of the first mask layer.

Dependencies are inferred from the claim text.