The present disclosure describes a method for the formation of gate stacks having two or more titanium-aluminum (TiAl) layers with different Al concentrations (e.g., different Al/Ti ratios). For example, a gate structure can include a first TiAl layer with a first Al/Ti ratio and a second TiAl layer with a second Al/Ti ratio greater than the first Al/Ti ratio of the first TiAl layer.