Methods for tuning threshold voltages of fin-like field effect transistor (FinFET) devices are disclosed herein. An exemplary integrated circuit device includes a high voltage n-type FinFET, a high voltage p-type FinFET, a low voltage n-type FinFET, and a low voltage p-type FinFET. Threshold voltages of the high voltage n-type FinFET and the high voltage p-type FinFET are greater than threshold voltages of the low voltage n-type FinFET and the low voltage p-type FinFET, respectively. The high voltage n-type FinFET, the high voltage p-type FinFET, the low voltage n-type FinFET, and the low voltage p-type FinFET each include a threshold voltage tuning layer that includes tantalum and nitrogen. Thicknesses of the threshold voltage tuning layer of the low voltage n-type FinFET and the low voltage p-type FinFET are less than thicknesses of the threshold voltage tuning layer of the high voltage n-type FinFET and the high voltage p-type FinFET, respectively.