A method for tuning the effective work function of a gate structure in a semiconductor device is described. The semiconductor device is part of an integrated circuit and the gate structure has a metal layer and a high-k dielectric layer separating the metal layer from an active layer of the semiconductor device. The method includes providing an interconnect structure of the integrated circuit on top of the gate structure, the interconnect structure comprising a layer stack comprising at least a pre-metal dielectric layer comprising a metal filled connecting via connected to the gate structure through the pre-metal dielectric layer, and the interconnect structure having an upper exposed metal portion; and, thereafter, exposing at least a portion of the upper exposed metal portion to a plasma under predetermined exposure conditions, to tune the effective work function of the gate structure.