PURPOSE: To suppress contact resistance between the first and second interconnections so that it becomes sufficiently small by removing the surface of the first conductor interconnection up to a prescribed depth after performing a process wherein a through hole is formed and then, by forming thin films for use in the second conductor interconnection in multilayer interconnections.

CONSTITUTION: In a state where a semiconductor substrate 1, a SiO2 film A2, the first Al interconnection 3, a SiO2 film B4, a photoresist film 5, a through hole 6, and a high resistance layer 7 are formed, reactive ion etching is carried out with a SiCl4 gas. Its treatment is performed on condition that an Al film of only about 0.1μm is etched. In this way, a part of about 0.1μm thick at the surface of a contact part of the first Al interconnection 3 is removed. (it is shown as an Al removal part 8). Then an aluminum metallic film is deposited in the same way that found conventionally and the second Al film 9 is formed. Thus, the high resistance layer 7 which has been formed at the surface of the contact part of the first Al interconnection 3 is removed together with the Al removal part 8 and the first Al interconnection 3 is connected with the second part Al film 9 at the part of the through hole 6 and then contact resistance between the above two parts can be suppressed so that it may become sufficiently small without exception.