Germanium nanowires (GeNWs) have importance in emerging device applications because of their high hole mobility. Reported here is the fabrication of GeNWs on a SiO2 insulator substrate from a phase separated lamellar PS-b-PMMA block copolymer (BCP) by a simple and reproducible method. The parent BCP film was selectively etched to remove PMMA block generating PS template which was then used to fabricate GeNWs using a thermal evaporation technique. XRD, Raman and TEM cross-section analysis reveal the formation of GeNWs on SiO2 substrates. Thermal treatment of the GeNWs was used to probe thermal stability and crystallisation properties. It was observed that thermal treatment of GeNWs resulted in red-shifts in the Raman spectra. The results demonstrate an exciting nanofabrication technique for creating high density nanowires for the nanoelectronic industry.