The technique of direct laser writing (DLW) is used to fabricate high-quality three-dimensional photonic crystals out of the photoresist SU-8. These polymeric 3D structures serve as templates for subsequent inversion and conversion techniques with silicon. Photonic band gaps of the Si replica as well as the inverse structures are measured. These measurements are further supported by numerical calculations. Among the experimental experimental techniques utilized are: DLW, atomic layer deposition (ALD), chemical vapor deposition (CVD) and reactive ion etching (RIE).