Semiconductor substrates and methods of manufacturing the same are provided. The semiconductor substrates include a substrate region, an insulation region and a floating body region. The insulation region is disposed on the substrate region. The floating body region is separated from the substrate region by the insulation region and is disposed on the insulation region. The substrate region and the floating body region are formed of materials having identical characteristics. The method of manufacturing the semiconductor substrate including forming at least one floating body pattern by etching a bulk substrate, separating the bulk substrate into a substrate region and a floating body region by etching a lower middle portion of the floating body pattern, and filling an insulating material between the floating body region and the substrate region.