PURPOSE: To prevent concentration of stress in an interconnection layer of aluminium or the like provided on a substrate and to reduce voids remarkably, by wet etching the interconnection layer for removing the edge corners on the top face of the interconnection layer before depositing an insulating film on the substrate having the interconnection layer.

CONSTITUTION: Before depositing an insulating film 3 such as a passivation film or interlayer insulation film on a substrate 5 having an interconnection layer 1 of aluminium or an aluminium alloy thereon, the edge corners 2 on the top face of the interconnection layer 1 are removed by wet etching. By wet etching the sharp corners of the interconnection layer 1 so as to round and smoothen them before depositing the insulation film 3 on the interconnection layer 1, stress from the insulation film 3 can be prevented from concentrating locally to a part of the interconnection layer 1 and voids 4 can be avoided. An etching solution for rounding the edge corners of the interconnection layer is a diluted solution such as nitric acid HNO3 or phosphoric acid H3PO4.