Semiconductor structure and fabrication method are provided. An exemplary method includes: providing a to-be-etched layer; forming a first mask material layer with a barrier region on the to-be-etched layer; forming a first mask groove and a second mask groove separated from each other in the first mask material layer and exposing two sidewalls of the barrier region along an extending direction of the first mask groove; forming barrier layers on exposed sidewalls of the barrier region; forming a first mask through hole in the barrier region of the first mask material layer by etching a portion of the barrier region of the first mask material layer by using the barrier layers as a mask; and forming a first groove, a second groove, and a through hole, by etching the to-be-etched layer using the barrier layers and the first mask material layer as a mask.