The present invention relates to a diffusion barrier layer for a semiconductor device and fabrication method thereof. The diffusion barrier layer according to the present invention is fabricated by forming a diffusion barrier layer containing a refractory metal material and an insulating material on an insulating layer and in a contact hole, wherein the insulating layer being partially etched to form the contact hole, is formed on a semiconductor substrate; and annealing the diffusion barrier layer. Therefore, an object of the present invention is to provide a diffusion barrier layer for a semiconductor device, which is of an amorphous or microcrystalline state and thermodynamically stable even at a high temperature since an insulating material is bonded to a refractory metal material in the diffusion barrier layer.