Abstract: A manufacturing method of a metal gate structure includes first providing a substrate having a dummy gate formed thereon. The dummy gate includes a high-K gate dielectric layer, a bottom barrier layer, a first etch stop layer and a sacrificial layer sequentially and upwardly stacked on the substrate. Then, the sacrificial layer is removed to form a gate trench with the first etch stop layer exposed on the bottom of the gate trench. After forming the gate trench, a first work function metal layer is formed in the gate trench.