The main theme of the thesis is to develop a COMS compatible process of three-dimensional (3D) germanium quantum dots (Ge QDs) array system. Using a simple method, “selectivity oxidation of polycrystalline SiGe” to form Ge QDs, combined with design and experiment of nano-patterned SiGe pillar structure to effectively control size, number and position of the Ge QDs. Then, we can fabricate a three-dimensional Ge QDs / silicon dioxide / silicon nitride arrays. We have studied the internal structure and optical properties of 3D Ge QDs array using scanning electron microscopy (SEM), transmission electron microscope (TEM), cathodoluminescence (CL) and Raman spectroscopy. In the future, we need to tailor 3D dense and size-tunable Ge QDs array, expect to boost the efficiency and optimize the device characteristics of solar cells and thermoelectric devices.