Semiconductor structure and method for forming the same

A method for forming a semiconductor structure, comprising:

• providing a to-be-etched layer;
• forming a core layer over the to-be-etched layer, wherein the core layer includes a first trench extending along a first direction;
• forming a sidewall spacer layer on a top surface of the core layer and on sidewalls and a bottom surface of the first trench;
• forming a block cut structure in the first trench after forming the sidewall spacer layer, wherein:
• the block cut structure extends through the first trench along a second direction;
• the second direction and the first direction are different;
• and
• the block cut structure includes a first block-cut layer and a second block-cut layer, wherein the first block-cut layer is disposed on sidewall surfaces of the second block-cut layer;
• and
• after forming the block cut structure, etching back the sidewall spacer layer until exposing the top surface of the core layer, thereby leaving a sidewall spacer on the sidewalls of the first trench.