Methods for fabricating semiconductor devices having through electrodes are provided. The method may comprise forming a via hole which opens towards an upper surface of a substrate and disconnects with a lower surface of the substrate; forming a via isolation layer which extends along an inner surface of the via hole and covers the upper surface of the substrate; forming a seed layer on the via isolation layer which extends along the via isolation layer; annealing the seed layer in-situ after forming the seed layer; forming a conductive layer, filling the via hole, by an electroplating using the seed layer; and planarizing the upper surface of the substrate to form a through electrode surrounded by the via isolation layer in the via hole.