To miniaturize metal columns. A semiconductor device includes a metal column (14) that extends in a stretching direction; a polymer layer (16) that surrounds the metal column from a direction crossing the stretching direction; and a guide (12) that surrounds the polymer layer in the crossing direction so as to be spaced from the metal column with the polymer layer interposed therebetween. A method for manufacturing semiconductor devices includes a step of filling a mixture (20) containing metal particles (22) and polymers (24) in a guide (12); and a step of subjecting the mixture to a heat treatment so that the polymers agglomerate to the guide to form a polymer layer (16) that makes contact with the guide and the metal particles agglomerate away from the guide with the polymer layer interposed therebetween to form a metal column (14) that stretches in a stretching direction of the guide from the metal particles.