PURPOSE: To prevent an interconnection from disconnecting due to step difference by a method wherein a contact layer is previously formed inside and around a groove of semiconductor substrate to form a layer structure of photoelement in the groove.

CONSTITUTION: A groove 2 is made in the surface of Si-GaAs substrate 1 as a semiconductor substrate. First, Si ion are implanted to form an n+type contact layer 8 of laser, an n+ type source drain region 9 of FET, an n type working region 10 of FET. Second, after covering the groove 2, an n type layer 3 and a p type layer 4 in a semiconductor laser layer structure comprising AlGaAs lamination structure are successively grown on the substrate 1. Third, the layers 4, 3 are etched until the surface of substrate 1 is exposed to flatten the substrate 1. Finally, a p type contact metal 5, an n type contact metal 6 and a gate electrode 13 are formed respectively on the layer 4, the layer 8 the region 9 and the region 10. Through these procedures, one side contact metal can be formed on the layer 4 around the groove 2 to make the substrate 1 planar for preventing the interconnection from disconnecting.