Abstract: The present disclosure provides a semiconductor structure and a method for forming the semiconductor structure. The method includes: providing a substrate; forming a mask layer on the substrate, wherein the mask layer exposes a part of a surface of the substrate; etching the substrate by a plasma etching process using the mask layer as a mask to form a plurality of trenches and an active region between the plurality of trenches; and forming an insulating layer in the plurality of trenches. The method according to some embodiments of the present disclosure can protect a corner region of the active region and improve a size stability of the active region.