The invention InP new active ion etching in the epitaxial layer can be very stable and smooth etching the raised structures, such as InAlAs, InGaAs, InP on a semiconductor substrate: relates to (RIE Reactive Ion Etching). RIE etching method presented in this invention is then caused the _{BCl 3, Cl 2, CH 4} , H 2 mixture plasma of an appropriate ratio to the etching proceeds at an appropriate degree of vacuum. Characteristic effects of the present invention is the fact that even at low temperatures can be clean and etch the low melting point is why conventional photoresist of below 100 ℃ also be used as a masking material. In addition, even in the case of silicon nitride (SiNx) that is commonly used as a mask material is only about 1/9 of the InAlAs etching rate. Another advantage of the invention is that very little softer similarities and etching the etch rate of giving a surface in the InAlAs, InGaAs, InP system, three kinds of materials. The present invention having such advantages will be used as an essential step in the manufacturing optical element in the optical communication, and the demand in the future.