SEMICONDUCTOR OPTICAL ELEMENT AND FABRICATION THEREOF

PURPOSE: To obtain a high quality high performance optical element or optical integrated element by enhancing the controllability of the compositional ratio of group III element in a mixed crystal semiconductor layer containing In there by growing a core layer having a large critical film thickness. CONSTITUTION: Using a semiconductor substrate 1 on which an insulating mask 2' having mask width varied partially in the direction of optical axis is formed along with a semiconductor mask 3, a semiconductor layer is formed including a thin clad layer 10 and core layers 5, 6 where the thickness of layer grown on the substrate 1 varies smoothly in the direction of optical axis. With such structure, controllability of the compositional ratio of group II element in a mixed crystal semiconductor layer is enhanced resulting in a semiconductor crystal having large thickness of critical film and a high quality optical integrated element.