The present invention provides a MOS device, which comprises: a substrate; an interface layer thin film formed on the substrate; a high k gate dielectric layer formed on the interface layer thin film; and a metal gate formed on the high k gate dielectric layer. The metal gate comprises, upwardly in order, a metal gate work function layer, an oxygen absorption element barrier layer, a metal gate oxygen absorbing layer, a metal gate barrier layer and a polysilicon layer. A metal gate oxygen absorbing layer is introduced into the metal gate for the purpose of preventing the outside oxygen from coming into the interface layer and absorbing the oxygen in the interface layer during a annealing process, such that the interface layer is reduced to be thinner and the EOT of MOS devices are effectively reduced; meanwhile, by adding an oxygen absorption element barrier layer, the “oxygen absorption element” is prevented from diffusing into the high k gate dielectric layer and giving rise to unfavorable impact thereon; in this way, the high k/metal gate system can be more easily integrated, and the performance of the device can be further improved accordingly.