FIN FIELD-EFFECT TRANSISTOR AND METHOD OF FORMING THE SAME

A method includes depositing a first work function layer over a first and second gate trench. The method includes depositing a second work function layer over the first work function layer. The method includes etching the second work function layer in the first gate trench while covering the second work function layer in the second gate trench, causing the first work function layer in the first gate trench to contain metal dopants that are left from the second work function layer etched in the first gate trench. The method includes forming a first active gate structure and second active gate structure, which include the first work function layer and the metal dopants left from the second work function layer in the first gate trench, and the first work function layer and no metal dopants left behind from the second work function layer, respectively.