A semiconductor device including an interconnection structure including a copper pad, a pad barrier layer and a metal redistribution layer, an interconnection structure thereof and methods of fabricating the same are provided. The semiconductor device includes a copper pad disposed on a first layer, a pad barrier layer including titanium disposed on the copper pad, an inorganic insulating layer disposed on the pad barrier layer, a buffer layer disposed on the inorganic insulating layer, wherein the inorganic insulating layer and the buffer layer expose a portion of the pad barrier layer, a seed metal layer disposed on the exposed buffer layer, a metal redistribution layer disposed on the seed metal layer, and a first protective layer disposed on the metal redistribution layer.