A photo-detecting device includes a buried doping layer of a first conductivity type and disposed at an upper portion of a silicon substrate. A first silicon epitaxial layer of first conductivity type is disposed on the buried doping layer, and a second silicon epitaxial layer of second conductivity type is disposed on the first silicon epitaxial layer. An isolation doping layer doped of first conductivity type is disposed at a predetermined region of the second silicon epitaxial layer to define a body region of second conductivity type. A silicon germanium epitaxial layer of second conductivity type is disposed on the body region.