A process for forming wiring over a migration preventing layer on a semiconductor substrate including forming a contact hole in a an insulation layer of the substrate and then filling the contact hole with an aluminum based alloy. A migration preventing layer is then formed, of a material which resists migration of atoms of the aluminum based alloy, over the surface of the aluminum based alloy. A wiring layer of aluminum is then formed over the migration preventing layer. In another embodiment, the contact hole may be provided with a first layer to prevent electron migration and a second layer which is a nitride of the first layer material.