The present disclosure provides a method for fabricating a semiconductor device. The method includes forming first, second, third, and fourth gate structures on a semiconductor substrate, each gate structure having a dummy gate, removing the dummy gate from the first, second, third, and fourth gate structures, thereby forming first, second, third, and fourth trenches, respectively, forming a metal layer to partially fill in the first, second, third, and fourth trenches, forming a first photoresist layer over the first, second, and third trenches, etching a portion of the metal layer in the fourth trench, removing the first photoresist layer, forming a second photoresist layer over the second and third trenches, etching the metal layer in the first trench and the remaining portion of the metal layer in the fourth trench, and removing the second photoresist layer.