According to an embodiment, a method of fabricating a photodiode device may include: growing an epitaxial layer on a first surface of a substrate, wherein the epitaxial layer is first type lightly doped; forming, in the substrate, a first type heavily doped region in contact with the first type lightly doped epitaxial layer; thinning the substrate from a second surface of the substrate opposite to the first surface to expose the first type heavily doped region; patterning the first type heavily doped region from the second surface side of the substrate to form a trench therein, that penetrates through the first type heavily doped region and extends into the epitaxial layer, to serve as a first electrode region of the photodiode device; and forming a second type heavily doped region at bottom of the trench, to serve as a second electrode region of the photodiode device.