Semiconductor structure and forming method thereof

The invention discloses a semiconductor structure and a forming method thereof, and the forming method comprises the steps: providing a substrate which comprises a substrate, a metal gate located on the substrate, and a first isolation structure which transversely cuts the metal gate, and a gate dielectric layer is formed between the first isolation structure and the metal gate; the first isolation structure at a first height is removed, a first isolation groove transversely cutting the metal gate is formed, and the gate dielectric layer located on the side wall of the first isolation groove is exposed by the first isolation groove; removing the gate dielectric layer on the side wall of the first isolation groove to form a second isolation groove; and forming a second isolation structure, wherein the second isolation groove is filled with the second isolation structure. The method not only can improve the device performance, but also is simple in process. 一种半导体结构及其形成方法，形成方法包括：提供基底，所述基底包括衬底、位于所述衬底上的金属栅极，以及横切所述