Abstract: An optically driven semiconductor device is disclosed which comprises a semiconductor substrate, a plurality of vertical field effect transistors formed on the substrate, and a plurality of optoelectric transducers formed on an insulating film above the respective transistors, wherein the transistors have the substrate in common as a drain. Also disclosed is an optically driven semiconductor device which comprises a semiconductor substrate, a vertical field effect transistor formed on the substrate and a solar cell formed on an insulating film above the substrate, wherein the solar cell is formed with a polycrystalline silicon layer or monocrystalline silicon layer grown by the chemical vapor deposition method. Moreover, there are disclosed optically coupled semiconductor relay devices using these optically driven semiconductor devices.