Semiconductor device and fabrication method thereof

A method for forming a semiconductor device, comprising:

• providing a semiconductor substrate, wherein the semiconductor substrate includes a first plug-cutting region and a fin-cutting region, and the fin-cutting region is located within the first plug-cutting region;
• forming an initial to-be-cut fin on the semiconductor substrate, wherein the initial to-be-cut fin is partially extended to the fin-cutting region;
• forming a gate structure across the initial to-be-cut fin over the semiconductor substrate, wherein the fin-cutting region and the first plug-cutting region are located on a side of the gate structure;
• forming a dielectric layer covering a sidewall of the gate structure over the semiconductor substrate and the initial to-be-cut fin;
• forming a cutting opening over the first plug-cutting region by removing a portion of the dielectric layer that is over the first plug-cutting region and a portion of the initial to-be-cut fin that is over the fin-cutting region, wherein a remaining initial to-be-cut fin forms a cutting fin on a side of the cutting opening, and a sidewall of the cutting opening exposes the gate structure;
• forming a cutting structure in the cutting opening;
• and
• forming a first plug structure in a remaining dielectric layer on a side of the gate structure, wherein the cutting structure cuts the first plug structure in a width direction of the cutting fin.