A packaging semiconductor device, such as a fan-out Wafer-Level Packaging (FOWLP) device, is fabricated by providing a semiconductor device (20) having conductive patterns (22) disposed on a first surface and then forming, on the conductive patterns, photoresist islands (24) having a first predetermined shape defined by a first critical width dimension and a minimum height dimension so that a subsequently-formed dielectric polymer layer (26) surrounds but does not cover each photoresist island (24), thereby allowing each photoresist island to be selectively removed from the one or more conductive patterns to form one or more via openings (28) in the dielectric polymer layer such that each via opening has a second predetermined shape which matches at least part of the first predetermined shape of the photoresist islands.