Disclosed are methods to form a FinFET diode of high efficiency, designed to resolve the degradation problem with a conventional FinFET diode arising from reduced active area, and a method of fabrication. The FinFET diode has a doped substrate, two spaced-apart groups of semiconductor fin structures, dielectric layers formed between the two groups and among the fin structures for insulation, a plurality of gate structures perpendicularly traversing both groups of the fin structures, and two groups of semiconductor strips respectively formed lengthwise upon the two groups of the fin structures. The two groups of semiconductor strips are doped to have opposite conductivity types, p-type and n-type. In an embodiment, the FinFET diode further has metal contacts formed upon the semiconductor strips. In another embodiment, the semiconductor strips may be integrally formed with the fin structures by epitaxial growth and in-situ doped.