the mask layer 6 by removing the resist layer 14 and cleaning the multilayer body the surface of the gaalas film constituting the mask layer 6 becomes the oxidized state subsequently the active layer 3 remaining in the circumference of the buried part a is removed by meltback and for example by a liquid phase epitaxy method lpe method a blocking layer 7 the conductivity type of which is p type composition ga 0 55 al 0 45 as carrier density 5 7 u00d7 10 17 cm 3 thickness 1 0 u03bcm a blocking layer 8 the conductivity type of which is n type ga 0 70 al 0 30 as 5 7 u00d7 10 17 cm 3 1 4 u03bcm and a blocking layer 9 the conductivity type of which is p type gaas 5 7 u00d7 10 17 cm 3 2 0 u03bcm are epitaxially grown in this sequence on the cladding layer 2 exposed to the circumference of the etched part a and thereby a regrowth b is formed fig1 c the etched part constitutes a buried part which is buried by the regrowth the regrowth constitutes a burying part conditions for crystal growth at this time are as follows conditions for meltback degree of undersaturation 2 u00b0 c at 805 u00b0 c 15.