Devices with lightly-doped semiconductor channels (e.g., FinFETs) need mid-gap (˜4.6-4.7 eV) work-function layers, preferably with low resistivity and a wide process window, in the gate stack. Tantalum carbide (TaC) has a mid-gap work function that is insensitive to thickness. TaC can be deposited with good adhesion on high-k materials or on optional metal-nitride cap layers. TaC can also serve as the fill metal, or it can be used with other fills such as tungsten (W) or aluminum (Al). The TaC may be sputtered from a TaC target, deposited by ALD or CVD using TaCl4 and TMA, or produced by methane treatment of deposited Ta. Al may be added to tune the threshold voltage.