A method of reducing electromigration in Cu interconnect lines by forming an interim layer of Ca-doped copper seed layer lining a via in a chemical solution and a semi conductor device thereby formed. The method reduces the drift velocity which then decreases the Cu migration rate in addition to void formation rate. The method comprises: depositing a Cu seed layer in the via; treating the Cu seed layer in a chemical solution, selectively forming a Cu--Ca--X conformal layer on the Cu seed layer, wherein X denotes at least one contaminant; and processing the Cu--Ca--X conformal layer, effecting a thin Cu--Ca conformal layer on the Cu seed layer; annealing the thin Cu--Ca conformal layer onto the Cu seed layer, removing the at least one contaminant, thereby forming a contaminant-reduced Cu--Ca alloy surface on the Cu seed layer; electroplating the contaminant-reduced Cu--Ca alloy surface with Cu, thereby forming a contaminant-reduced Cu--Ca/Cu interconnect structure; annealing the at least one contaminant-reduced Cu--Ca/Cu interconnect structure, thereby forming at least one virtually void-less and contaminant-reduced Cu--Ca/Cu interconnect structure; and chemical mechanical polishing the at least one virtually void-less and contaminant-reduced Cu--Ca/Cu interconnect structure.