Semiconductor device with oxygen-diffusion barrier layer and method for fabricating same

Methods are provided for fabricating a transistor. An exemplary method involves depositing an oxide layer overlying a layer of semiconductor material, forming an oxygen-diffusion barrier layer overlying the oxide layer, forming a layer of high-k dielectric material overlying the oxygen-diffusion barrier layer, forming a layer of conductive material overlying the layer of high-k dielectric material, selectively removing portions of the layer of conductive material, the layer of high-k dielectric material, the oxygen-diffusion barrier layer, and the oxide layer to form a gate stack, and forming source and drain regions about the gate stack. When the conductive material is an oxygen-gettering conductive material, the oxygen-diffusion barrier layer prevents diffusion of oxygen from the deposited oxide layer to the oxygen-gettering conductive material.