Abstract We have recently developed a Si1-xGex sputter epitaxy method for next-generation high-speed Si/Si1-xGex devices. With this method, we have succeeded in controlling the strain-relaxation behaviors and obtaining good crystalline Si1-xGex layers. We have obtained smooth and uniformly strained Si (s-Si), on our proposed quadruple strain-relaxed buffer, which also exhibits a high electron mobility enhancement by strain. With this method, we have also succeeded in forming a very flat Ge layer directly on Si (001). Using the flat Ge layer, we have first fabricated a Si-barrier/Ge-well single-well hole-tunneling resonant tunneling diode which is an ideal structure and exhibits a high peak-to-valley current ratio at room temperature. The flat s-Si, Si1-xGex, and Ge layers formed on Si by the sputter epitaxy method and then the sputter epitaxy method are useful to be applied to next-generation high-speed and high-density Si/Si1-xGex devices as an environmentally light-load method.