Novel synthesis method to fabricate Si-added amorphous carbon (a-C) nano-particles could be established using the radio-frequency plasma-enhanced vapor deposition (r.f.-PeCVD) system (13.56 MHz, SAMCO Co., Ltd, BPD-1) with porous aluminum plate loaded between the cathode and the anode. The mechanism of nano particles formation was clarified by verifying the relation between the shape of particles and the condition of r.f.-PeCVD such as r.f. power, chamber pressure and plate thickness. Si-added a-C nano-particles with minimum diameter of 14.8 nm could be fabricated with r.f. power of 50 W, chamber pressure of 60 Pa and plate thickness of 0.7 mm. These nano particles showed photon-to-current conversion functionality under 360 nm irradiation, and can be applied for photo electronic device in nano-meter size. sp2 impurities that causes the degradation of semiconductor properties could be reduced by the decrease of r.f. power and the increase of flow rate of H2 gas during CVD synthesis. Semiconductor properties such as carrier mobilities of Si-added a-C nano-particle were able to be improved up to those of practically-used semiconductor in photo electronic devices.