Abstract: Indirect energy band structure can be transformed to a direct structure in nano－scale Ge quantum dots materials self－assembled on a Si substrate, as a result of the three dimensional quantum confinement effect. Enhancement of the exciton behavior and radiative transition via the energy band gap present a possible way for development of effective Si－based active photonic devices and the realization of ordered and uniform Ge quantum dot arrays. Their controllable fabrication, will be helpful for the development of a new generation of Si－based electron－wave quantum devices. A review is presented on the recent development of self－assembled Ge/Si quantum dots and possible wide applications. With reference for our recent research results, emphasis is given to the morphological evolution of Ge grown on a Si (001) substrate and their dynamical process, derivation of the type－Ⅱenergy band diagram of Ge/Si quantum dots through photo－luminescence studies, and our efforts to fabricate ordered and uniform Ge/Si quantum dot arrays with a Si pattern substrate.