Semiconductor structure and method for forming the same

A method for forming a semiconductor structure, comprising:

• forming a first active region over a substrate;
• forming an isolation structure over the substrate to surround a lower portion of the active region;
• forming a dummy gate structure across the first active region and the isolation structure;
• forming gate spacer layers alongside the dummy gate structure;
• replacing the dummy gate structure with a gate stack;
• etching the gate stack, first active region and the isolation structure to form a trench;
• and
• forming a first cutting structure in the trench, wherein a first portion of the first cutting structure extending into the isolation structure is wider than a second portion of the first cutting structure extending into the first active region.

A semiconductor structure, comprising:

• an active region extending in a first horizontal direction;
• an isolation structure surrounding the active region;
• and
• a cutting structure extending in a second horizontal direction and including a first portion penetrating through the isolation structure and a second portion penetrating through the active region, wherein the first portion of the cutting structure has a first dimension in the first horizontal direction, the second portion of the cutting structure has a second dimension in the first horizontal direction, and the first dimension is greater than the second dimension.