The present invention provides a semiconductor device comprising a metal interconnect having considerably improved electromigration resistance and/or stress migration resistance. The copper interconnect 107 comprises a silicon-lower concentration region 104 and a silicon solid solution layer 106 disposed thereon. The silicon solid solution layer 106 has a structure, in which silicon atoms are introduced within the crystal lattice structure that constitutes the copper interconnect 107 to be disposed within the lattice as inter-lattice point atoms or substituted atoms. The silicon solid solution layer 106 has the structure, in which the crystal lattice structure of copper (face centered cubic lattice; lattice constant is 3.6 angstrom) remains, while silicon atoms are introduced as inter-lattice point atoms or substituted atoms.