Silicon avalanche photodiode (APD) is a highly sensitive semiconductor photo sensor that uses the photoelectric effect converting light to electric charge. APD has high a gain through avalanche mul-tiplication in its p-n junction. APD also has various preferable characteristics such as high quantum efficiency, large dynamic range, light-weight form-factor, robustness and insensitivity to magnetic fields as well as low light measurement capability thanks to its gain of ~ 100. As a monolithic device, however, it usually has size of ~ 5 x 5 mm2. The APD sensor has appealed to various fields of exper-imental physics due to its low light detection. But its usage is still limited because of its small surface area. The photo sensor in an experiment usually is required to cover a large area. In this study, the p-n junction of an APD was simulated with a sufficiently strong electric field enabling avalanche breakdown at ~ 400 V. We have designed large area APD sensors with channels of 5 x 5 and 10 x 10 to cover a wide area of ~ 5 x 5 cm2. The sensors were fabricated on a 6-inch n-type silicon wafer in about 140 steps. We present the simulation, design and fabrication result for multi-channel silicon APD sensors manufactured in Korea.