like and a reflective film of al 2 o 3 u03b1 si or sio 2 is formed on the end surfaces to obtain a desired reflectance by the above described steps the semiconductor optical device according to the first embodiment is manufactured as described above since the active layer 15 in not exposed when the striped structure 18 is formed the active layer 15 containing elemental aluminum is not exposed to the external air and chemical solutions therefore the favorable characteristics and high reliability of semiconductor optical devices can be ensured a method for manufacturing a semiconductor optical device according to the second embodiment of the present invention will be described referring to the drawings here the case of a semiconductor laser will be described as an example of semiconductor optical devices first in the same manner as in the first embodiment steps shown in fig1 to 6 are carried out next as shown in fig9 in a crystal growing apparatus for forming burying layers the p type inp clad layer 12 that covers the sides of the active layer 15 is removed by dry etching using a halogen containing gas such as hcl to expose the sides of the active layer.