Silicon inverse woodpile photonic crystals are fabricated for the first time. Our approach, which is based on direct laser writing of polymeric templates and a novel silicon single-inversion procedure, leads to high-quality structures with gap/midgap ratios of 14.2%, centered at a wavelength of 2.5 mu m. It is shown that gap/midgap ratios as large as 20.5%, centered at 1.55 mu m, may become possible in the future.