a semiconductor device has a wiring slot and two wiring layers connected by a via hole . the semiconductor device is formed using a photodegradable polymer film that degrades under uv radiation . an incidence angle θ of radiation rays in the irradiating step with respect to a perpendicular direction of a surface of the substrate , fulfills the relationship tan θ ≧ h + h ′/ 2 wherein d is a depth of the wiring slot , d ′ is a thickness of the photoresist film , h is a diameter of the via hole in a opening of the wiring slot , and h ′ is the width of the wiring slot .