BACKGROUND

Transistors are basic building elements in integrated circuits. In previous development of the integrated circuits, Fin Field-Effect Transistors (FinFETs) are formed to replace planar transistors. In the formation of FinFETs, semiconductor fins are formed, and dummy gates are formed on the semiconductor fins. Gate spacers are formed on the sidewalls of the dummy gate stacks. The dummy gate stacks are then removed to form trenches between the gate spacers. Replacement gates are then formed in the trenches.

