The fundamental problems of the growth of III-V compounds on a Si substrate were overcome. As a result, structural defect-free GaPN and InGaPN layers were grown on a Si substrate. LEDs and Si MOSFETs, which are elemental devices for OEICs, were monolithically merged in a single chip. The developed processing flow was based on a conventional MOSFET processing flow. The growth and fabrication process technologies are effective for the realization of monolithic OEICs.