Method for forming stackable semiconductor device packages including openings with conductive bumps of specified geometries

In one embodiment, a manufacturing method includes: (1) applying a first electrically conductive material to an upper surface of a substrate to form first conductive bumps; (2) electrically connecting a semiconductor device to the upper surface of the substrate; (3) applying a molding material to form a molded structure covering the first conductive bumps and the semiconductor device, upper ends of the first conductive bumps being recessed below an upper surface of the molded structure; (4) forming openings adjacent to the upper surface of the molded structure, the openings exposing the upper ends of the first conductive bumps; (5) applying, through the openings, a second electrically conductive material to form second conductive bumps; and (6) forming cutting slits extending through the molded structure and the substrate.