PURPOSE: To prevent oxidation of interconnections made of polyside, to eliminate a stress at the interconnection and an insulating film formed around the interconnection and to obtain high yield and high reliability by increasing a thickness of a layer insulating film on the interconnection of the polyside thicker than that of a layer insulating film on the other interconnection.
CONSTITUTION: The semiconductor device comprises at least three-layers or more of interconnections. In such a device, a thickness Ta of a layer insulating film between a first interconnection 107 and a second interconnection of polyside formed of a polycrystalline silicon film 105 and a silicide film 106 formed under the interconnection 107 is thicker than that Tb of a second layer insulating film formed between a third interconnection 103 and the interconnection 107 formed under the second interconnections 105, 106. Thus, oxygen is diffused in the interlayer insulating film by later heat treating in an atmosphere containing oxygen to increase a time arriving at the interconnection, thereby scarcely oxidizing due to reaction of the silicon with the oxygen in the interconnection.
