Methods for tuning threshold voltages of fin-like field effect transistor devices are disclosed herein. An exemplary method includes forming a first opening in a first gate structure and a second opening in a second gate structure. The first gate structure is disposed over a first fin structure, and the second gate structure is disposed over a second fin structure. The method further includes filling the first opening and the second opening by forming a gate dielectric layer, forming a threshold voltage tuning layer over the gate dielectric layer, etching back the threshold voltage tuning layer in the second opening, forming a work function layer over the threshold voltage tuning layer, and forming a metal fill layer over the work function layer. The threshold voltage tuning layer includes tantalum and nitrogen. The etching back uses a tungsten-chloride containing precursor.