Under the terms of the Creative Commons Attribution (CC BY) license to their work.-- et al. ; A thin, flat, and single crystal germanium membrane would be an ideal platform on which to mount sensors or integrate photonic and electronic devices, using standard silicon processing technology. We present a fabrication technique compatible with integrated-circuit wafer scale processing to produce membranes of thickness between 60 nm and 800 nm, with large areas of up to 3.5 mm2. We show how the optical properties change with thickness, including appearance of Fabry-Pérot type interference in thin membranes. The membranes have low Q-factors, which allow the platforms to counteract distortion during agitation and movement. Finally, we report on the physical characteristics showing sub-nm roughness and a homogenous strain profile throughout the freestanding layer, making the single crystal Ge membrane an excellent platform for further epitaxial growth or deposition of materials. ; This work was carried out under the RCUK Basic Technology Programme supported by research Grant Nos. EP/F040784/1, EP/J001074/1, and EP/L007010/1. It also received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement NANOFUNCTION n°257375 alongside funding from TAPHOR (MAT2012–31392) and FP7 Project MERGING (Grant No. 309150). Vibrational property measurements were funded by the ERC under Grant No. 202735, NonContactUltrasonic. ; Peer Reviewed