The fascinating properties of ionic liquids make it possible to synthesize semiconductor nanostructures via a simple and low-cost electrochemical pathway. The present paper summarizes our recent work on the synthesis of Si, Ge, and Si_xGe_1–x nanostructures from ionic liquids: thin films, nanowires and photonic crystals. We also introduce our first results on the template-assisted electrodeposition of Si_xGe_1–x photonic crystals from 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf₂N) ionic liquid, and some optical measurements on the previously prepared Ge photonic crystals. Our results confirm that electrochemistry in ionic liquids is excellently suited to the synthesis of high-quality semiconductor nanostructures.