Deposition of titanium-aluminum layers

Transistors having a work function layer and methods of fabricating thereof are disclosed herein. The work function layer includes aluminum and titanium layers which are deposited in separate atomic layer deposition (ALD) operations. The depositions of the titanium layers and the aluminum layers may be separated by a purge operation or even performed in different ALD chambers. The work function layer may include alternating sets of titanium layers and sets of aluminum layers, thereby forming a nanolaminate structure. As such, a ratio of titanium to aluminum may be controlled and varied as needed throughout the thickness of the work function layer. For example, the work function layer may be titanium rich at the surface facing the gate dielectric in order to reduce or prevent diffusion of aluminum into the gate dielectric.