The present disclosure provides a method for forming a semiconductor structure. The method includes the following operations. A metal layer is formed. An adhesion-enhancing layer is formed over the metal layer. A dielectric stack is formed over the adhesion-enhancing layer. A trench is formed in the dielectric stack. A barrier layer is formed conforming to the sidewall of the trench. A high-k dielectric layer is formed conforming to the barrier layer. A sacrificial layer is formed conforming to the high-k dielectric layer.