The present invention relates to the field of semiconductor manufacturing. The present invention provides a method of manufacturing a semiconductor device, which comprises: providing a semiconductor substrate; forming an interface layer, a gate dielectric layer and a gate electrode on the substrate; forming a metal oxygen absorption layer on the gate electrode; performing a thermal annealing process on the semiconductor device so that the metal oxygen absorption layer absorbs oxygen in the interface layer and the thickness of the interface layer is reduced. By means of the present invention, the thickness of the interface layer can be reduced on one hand, and on the other hand the metal in the metal oxygen absorption layer is made to diffuse into the gate electrode and/or the gate dielectric layer through the annealing process, which further achieves the effects of adjusting the effective work function and controlling the threshold voltage.