PURPOSE: To increase the number of quantum fine line layers by causing the respective left and right inner slopes of the second grooves of a second groove row to have different crystal faces.

CONSTITUTION: By an etching process with a mask 4 for a semiconductor substrate 1 as a mask, a first groove row 6, in which first grooves 5 are sequentially disposed at predetermined intervals, is formed in the semiconductor substrate 1. Then, the mask 4 is removed from the principal surface of the semiconductor substrate 1, and a semiconductor layer 7 is formed as a buffer layer. In this case, by properly selecting the pressure in the container, the temperature of the semiconductor substrate and the like, the semiconductor layer 7 as a buffer layer is formed so that the upper surface thereof has a second groove row in which second grooves 8 of a V-like section are extending in stripes and the left and right inner slopes 8L and 8R are respectively corresponding to a (001)-face and (111)B-face over the full length thereof.