Embodiments disclosed herein relate to a pre-deposition treatment of materials utilized in metal gates of different transistors on a semiconductor substrate. In an embodiment, a method includes exposing a first metal-containing layer of a first device and a second metal-containing layer of a second device to a reactant to form respective monolayers on the first and second metal-containing layers. The first and second devices are on a substrate. The first device includes a first gate structure including the first metal-containing layer. The second device includes a second gate structure including the second metal-containing layer different from the second metal-containing layer. The monolayers on the first and second metal-containing layers are exposed to an oxidant to provide a hydroxyl group (—OH) terminated surface for the monolayers. Thereafter, a third metal-containing layer is formed on the —OH terminated surfaces of the monolayers on the first and second metal-containing layers.