A process is provided for fabricating a semiconductor device having a germanium nanofilm layer that is selectively deposited on a silicon substrate in discrete regions or patterns. A semiconductor device is also provided having a germanium film layer that is disposed in desired regions or having desired patterns that can be prepared in the absence of etching and patterning the germanium film layer. A process is also provided for preparing a semiconductor device having a silicon substrate having one conductivity type and a germanium nanofilm layer of a different conductivity type. Semiconductor devices are provided having selectively grown germanium nanofilm layer, such as diodes including light emitting diodes, photodetectors, and like. The method can also be used to make advanced semiconductor devices such as CMOS devices, MOSFET devices, and the like.