PURPOSE: To control the width of a strip to an optimum by etching a region smaller than a specific area in a substrate plane.

CONSTITUTION: Hot CVD SiO2 is masked and etched to form a strip 25 of SiO2 by photolithography. After resist 30a is removed, a resist pattern 30b is formed by photolithography. Side grooves 33a and 33b are formed by etching with aqueous solution of Br and HBr using the resist 30b and SiO2 as a mask. The resist 30b is removed. The SiO2 is used as a mask to selectively grow a current constriction layers 26a and 26b of n-GaAs by MOCVD. After the SiO2 25 is removed, a p-GaAs contact layer 27 is grown. In this way, a wafer is subjected to main processes. Evaporation is carried out to deposit AuZn on the p-GaAs layer 27 and AuGe on the n-GaAs layer.