A method of forming a semiconductor structure includes performing a first deposition process to deposit a first high-K dielectric layer on a surface of a substrate, performing an interface formation process to form an interfacial layer on the surface of the substrate, performing a second deposition process to deposit a second high-K dielectric layer on the interfacial layer, performing a plasma nitridation process to insert nitrogen atoms in the first high-K dielectric layer and the second high-K dielectric layer, and performing an anneal process to passivate chemical bonds in the first high-K dielectric layer and the second high-K dielectric layer.