Methods for selectively depositing a metal layer over a gate structure and semiconductor devices formed by the same are disclosed. In an embodiment, a semiconductor device includes a channel region over a semiconductor substrate; a gate structure over the channel region; a gate spacer adjacent the gate structure; a first dielectric layer adjacent the gate spacer; a barrier layer contacting a top surface of the gate spacer and a side surface of the first dielectric layer, the barrier layer including a nitride; and a metal layer over the gate structure adjacent the barrier layer, the metal layer having a first width equal to a second width of the gate structure.