Semiconductor structure and fabrication method thereof

A fabrication method of a semiconductor structure, comprising:

• providing a substrate, wherein the substrate comprises a first region, a second region, and an isolation region disposed between the first region and the second region;
• forming a first fin, a second fin, and a third fin over the first region, the second region, and the isolation region, respectively;
• forming a high-K dielectric layer on top and sidewall surfaces of the first fin, the second fin, and the third fin;
• and
• forming a gate structure on the high-K dielectric layer and across the first fin, the second fin, and the third fin, wherein:
• the gate structure comprises a first work function layer disposed over the first region and a first portion of the isolation region, and a second work function layer disposed over the second region and a second portion of the isolation region, and
• an interface where the first work function layer is in direct contact with the second work function layer is located over a top surface of the high-K dielectric layer on the top surface of the third fin.