A method of fabricating a semiconductor device prevents agglomeration of a seed metal layer in a recess. A recess is formed in a dielectric layer formed on or over a wafer. A seed metal layer (e.g., Cu or Cu alloy) is then formed on a bottom face and an inner side face of the recess. Subsequently, a surface of the seed metal layer is oxidized by exposing the surface of the seed metal layer to an oxygen-containing gas or the atmospheric air before agglomeration of the seed metal layer occurs, thereby forming an oxide layer in the surface of the seed metal layer. A filling metal (e.g., Cu or Cu alloy) is plated on the oxide layer of the seed metal layer while using the seed metal layer whose surface is oxidized as an electrode, thereby filling the recess with the metal.