Semiconductor device and fabrication method thereof

A fabrication method of a semiconductor device, comprising:

• providing a base substrate, the base substrate including a substrate and a plurality of fins discrete from each other on the substrate;
• forming a dummy gate structure on the base substrate, wherein the dummy gate structure including a first portion in a first region and a second portion in a second region, and a length of the first portion of the gate structure in the first region is larger than a length of the second portion of the gate structure in the second region;
• etching part of the first portion of the dummy gate structure in the first region, to form a plurality of openings in the dummy gate structure in the first region, wherein bottoms of the plurality of openings expose a surface of the base substrate;
• forming a stop layer in each opening of the plurality of openings to fill up the opening, the plurality of stop layers being made of a material including SiCBN;
• removing the dummy gate structure to form a gate opening in the base substrate;
• forming an initial gate structure in the gate opening;
• and
• planarizing the initial gate structure until exposing top surfaces of the plurality of stop layers, to form a gate structure;
• wherein:
• the gate structure includes a gate dielectric layer on top surfaces and sidewalls of the plurality of fins, a work function layer on the gate dielectric layer, and a gate electrode layer on the work function layer;
• and
• the gate dielectric layer is in contact with a bottom surface of the plurality of stop layers, the work function layer and the gate electrode layer are in contact with sidewall surfaces of the plurality of stop layers.