Semiconductor device having a double-layer interconnection structure

A semiconductor device having a double-layer interconnection with contact portions between first and second metal films, each having a multi-layered structure, covered with at least a silicon nitride film is provided wherein an electromigration characteristic at the contact portions is improved. The improvement is achieved by defining a value obtained by multiplying a thickness of the silicon nitride film by a stress of the nitride film formed at the contact portions is not larger than 2/5 of a value obtained by multiplying a thickness of the silicon nitride film by a stress of the nitride film formed at non-contact portions. By this, the stress exerted on the second metal film is reduced to improve the electromigration life at the contact portions by about one order of magnitude. The first and second metal films, respectively, have a multi-layered structure including a sub-layer made of Al or Al alloys.