In recent decades, metal-semiconductor-metal (MSM) photodetector for optical fiber communication applications have been studied extensively. The dark current in MSM PD is an important parameter that can be reduced by schottky barrier enhancement and fabrication process. By employing a benzocyclobuten (BCB) sidewall passivation process, the leakage issue between Schottky metal fingers and mesa sidewalls can be avoided. Moreover, the parasitic capacitance can also be decreased due to the low dielectric constant of BCB. The BCB passivation process decreases the dark current density from 11 nA/μm 2 to 5.7pA/μm2.