This chapter deals with the microwave processing of a powder mixture of silicon and germanium (group IV semiconductors) which has resulted in the growth of nanostructures of Si1-xGex (0 ≤ x ≤ 0.25) alloys. The role of powder particle size and its shape are found to be crucial in the formation of these nanostructures by employing the MW processing in single mode. The reaction atmosphere—air or Argon—has played a definitive role in controlling the morphology of the resulting semiconducting alloys (nanoparticles and nanowires). This technique of material processing has reduced the equilibrium temperature of SiGe alloy formation considerably. A new mechanism of interaction of MW with semiconductors has been briefly described at the end of this chapter.