Abstract: A semiconductor film is formed on a GaAs substrate (semiconductor substrate). An SiO2 film (insulating film) is formed on the semiconductor film, and the SiO2 film is patterned. The semiconductor film is etched using the SiO2 film as a mask to form a mesa structure. The surface of the SiO2 film is treated by ashing, using SF6 gas (fluorine-containing gas), to terminate the surface of the SiO2 film with fluorine. The mesa structure is selectively buried with a III-V compound semiconductor film, using the SiO2 film having the surface that has been terminated by fluorine, as a mask.

Abstract: A semiconductor film is formed on a GaAs substrate (semiconductor substrate). An SiO2 film (insulating film) is formed on the semiconductor film, and the SiO2 film is patterned. The semiconductor film is etched using the SiO2 film as a mask to form a mesa structure. The surface of the SiO2 film is treated by ashing, using SF6 gas (fluorine-containing gas), to terminate the surface of the SiO2 film with fluorine. The mesa structure is selectively buried with a III-V compound semiconductor film, using the SiO2 film having the surface that has been terminated by fluorine, as a mask.

Abstract: A semiconductor optical modulator includes an active region including a multi quantum well structure. Thereby, it is possible to absorb laser light having two polarization wave modes to a high degree as well as increase the number of quantum wells without fracturing the crystal, thereby providing a modulator having no polarization plane dependency and an increased extinction ratio. Further, a plurality of electrodes, each having an aperture, are provided at an upper surface and an electrode having the same number of apertures as on the upper surface is provided at a lower surface opposite the other electrodes. Multiple laser light beams incident from the apertures at the upper surface are respectively modulated and output from the apertures at the opposing lower surface. Therefore, in the active region, laser light beams including both TE and TM modes are absorbed or transmitted by the modulator without dependency on their respective polarization planes.