Abstract: A modulator including: a Mach-Zehnder modulator that includes an optical waveguide disposed on a substrate, the optical waveguide including an electrode thereon; a resin layer disposed on the substrate, the resin layer embedding the optical waveguide, the resin layer having a groove arranged besides the optical waveguide; a termination resistor disposed on the substrate in the groove of the resin layer; and a first wiring disposed on the resin layer, the first wiring being connected to the termination resistor and the electrode of the optical waveguide.

Abstract: An optical semiconductor device including: a substrate having a principal surface; a first and a second optical waveguides disposed on the principal surface of the substrate, the first and second optical waveguides extending in a first direction, the second optical waveguide being arranged adjacent to the first optical waveguide in a second direction intersecting with the first direction; a first and a second signal electrodes disposed on the first and second optical waveguides; a resistor disposed on the principal surface, the resistor being arranged between the first optical waveguide and the second optical waveguide, the resistor being electrically connected to the first signal electrode and the second signal electrode; a resin layer disposed on the principal surface, top surfaces of the first and second signal electrodes, and the resistor; and a capacitor disposed on the resin layer, the capacitor being electrically connected to the resistor through an opening of the resin layer.

Abstract: A semiconductor optical modulator includes a substrate having a principal surface; a waveguide disposed on the principal surface of the substrate, the waveguide extending in a first direction; a first electrode disposed on the waveguide, the first electrode being in contact with an upper surface of the waveguide; a first wiring connected to the first electrode, the first wiring extending in a second direction intersecting the first direction; a build-up portion connected to the first wiring; a second wiring connected to the build-up portion, the second wiring extending in a plane parallel to the principal surface of the substrate; and a resin layer disposed on the substrate, the resin layer embedding the first wiring and the build-up portion. The build-up portion extends along a third direction, the third direction intersecting perpendicularly to the principal surface of the substrate. The second wiring is disposed on the resin layer.

Abstract: A semiconductor optical waveguide device includes a substrate having a first area and a second area, and first, second, and semiconductor mesas on the substrate. The first semiconductor mesa includes a cladding layer and a first mesa portion on the second area, the first mesa portion including first and second portions. The second semiconductor mesa includes an intermediate layer, a first core layer, and first and second mesa portions on the first and second areas, respectively. The third semiconductor mesa includes a second core layer, and first and second mesa portions having a greater width than that of the second semiconductor mesa. The first portion of the first semiconductor mesa has a substantially same width as the second mesa portion of the second semiconductor mesa. The first core layer is optically coupled to the second core layer through the intermediate layer disposed between the first and second core layers.

Abstract: A method for manufacturing a semiconductor optical device includes the steps of growing a stacked layer including lower and upper core layers, a first upper region including a non-doped layer, a second upper region including a p-type layer, and a cap layer; forming an upper mesa by etching the stacked layer; selectively etching the cap layer in the upper mesa on the first and second regions; forming a mask on the upper mesa in the second and third regions; and etching the upper mesa using the mask so as to form first to fourth mesa portions. The first and fourth mesa portions are formed by etching the first and second upper regions, and the second upper region and the cap layer, respectively. The second and third mesa portions are formed by etching the first and second upper regions, and the second upper region and the cap layer, respectively.

Abstract: A method for producing a spot-size convertor includes the steps of preparing a substrate; forming a stacked semiconductor layer including first and second core layers on the substrate; forming a mesa structure by etching the stacked semiconductor layer using a first mask, the mesa structure including a side surface and a bottom portion of the first core layer; forming a protective mask covering the side surface; etching the bottom portion using the protective mask to form a top mesa; and forming a bottom mesa by etching the second core layer using a second mask. The top mesa includes the first core layer and a portion having a mesa width gradually reduced in a first direction of a waveguide axis. The bottom mesa includes the second core layer and a portion having a mesa width gradually reduced in a second direction opposite to the first direction.

Abstract: A method for manufacturing a Mach-Zehnder modulator includes the steps of forming a stacked semiconductor layer, the stacked semiconductor layer including a first conductivity type semiconductor layer, a core layer and a second conductivity type semiconductor layer, forming a waveguide mesa, the waveguide mesa having a first portion, a second portion and a third portion arranged between the first and second portions; forming a buried region on the waveguide mesa; forming an opening in the buried region on the third portion by etching the buried region using a mask; etching the second conductivity type semiconductor layer in the third portion through the buried region as a mask; and removing the buried region after etching the second conductivity type semiconductor layer. In the step of etching the second conductivity type semiconductor layer, the buried region covers a side surface of the third portion of the waveguide mesa.

Abstract: A method for manufacturing a semiconductor optical waveguide device includes the steps of forming a waveguide mesa having first and second portions by etching a stacked semiconductor layer through a first mask; forming a dummy buried region embedding a top surface and side surfaces of the waveguide mesa; forming a second mask on the dummy buried region, the second mask having an opening on the first portion and having a pattern on the second portion; forming a third mask having an opening that reaches a top surface of the first portion, the third mask including a dummy buried mask formed by etching the dummy buried region through the second mask; forming an upper mesa by etching the waveguide mesa through the third mask; and after removing the third mask, forming a lower mesa by etching the stacked semiconductor layer, the lower mesa having a greater width than that of the upper mesa.

Abstract: A method for producing optical semiconductor devices includes: forming a stacked semiconductor layer on a device substrate to provide an epitaxial substrate having a size corresponding to a section arrangement; forming, on the epitaxial substrate, a mask having a pattern for a semiconductor mesa and for a trench of at least one optical semiconductor device, a width of the trench in the pattern being determined according to a trench width map in which trench width is based upon an in-plane distribution of the thickness of a resin layer of the at least one device, and upon a correlation between the thickness of the resin layer and the trench width; forming a trench structure including the semiconductor mesa and the trench by etching the stacked semiconductor layer using the mask; forming a resin layer on the trench structure; and forming an opening on the semiconductor mesa by etching the resin layer.

Abstract: A method for producing an optical semiconductor device includes the steps of determining a wafer size to make a section arrangement including a plurality of sections in each of which the optical semiconductor device including a semiconductor mesa is formed; obtaining an in-plane distribution of a thickness of a resin layer on a wafer; obtaining a correlation between a thickness of a resin layer and a trench width; forming a trench width map using the in-plane distribution of the thickness and the correlation; preparing an epitaxial substrate by forming a stacked semiconductor layer; forming, on the epitaxial substrate, a mask based on the trench width map; forming a trench structure including the semiconductor mesa by etching the stacked semiconductor layer using the mask; forming a resin layer on the trench structure; and forming an opening on the semiconductor mesa by etching the resin layer.

Abstract: A method for manufacturing an optical semiconductor device includes the steps of preparing a substrate product including a semiconductor layer, a mesa structure, and a protective layer; forming a buried layer composed of a resin on the substrate product; forming a first opening in the buried layer on the mesa structure; forming a second opening in the buried layer on the semiconductor layer; exposing the mesa structure and the semiconductor layer by etching the protective layer; forming a first electrode in the first opening; and forming a second electrode in the second opening. The step of forming the second opening includes a first etching step including etching the buried layer using a first resist mask for forming a recess and a second etching step including etching the buried layer using a second resist mask having an opening pattern which has an opening width not smaller than that of the recess.

Abstract: A method for fabricating a semiconductor device includes performing thermal cleaning for a surface of a silicon substrate in an atmosphere including hydrogen under a condition that a thermal cleaning temperature is higher than or equal to 700° C. and is lower than or equal to 1060° C., and a thermal cleaning time is longer than or equal to 5 minutes and is shorter than or equal to 15 minutes; forming a first AlN layer on the substrate with a first V/III source ratio, the forming of the first AlN layer including supplying an Al source to the surface of the substrate without supplying a N source, and supplying both the Al source and the N source; forming a second AlN layer on the first AlN layer with a second V/III source ratio that is greater than the first ratio; and forming a GaN-based semiconductor layer on the second AlN layer.

Abstract: A method for manufacturing a semiconductor optical device includes the steps of growing a stacked layer including lower and upper core layers, a first upper region including a non-doped layer, a second upper region including a p-type layer, and a cap layer; forming an upper mesa by etching the stacked layer; selectively etching the cap layer in the upper mesa on the first and second regions; forming a mask on the upper mesa in the second and third regions; and etching the upper mesa using the mask so as to form first to fourth mesa portions. The first and fourth mesa portions are formed by etching the first and second upper regions, and the second upper region and the cap layer, respectively. The second and third mesa portions are formed by etching the first and second upper regions, and the second upper region and the cap layer, respectively.

Abstract: A method for producing a spot-size convertor includes the steps of preparing a substrate; forming a stacked semiconductor layer including first and second core layers on the substrate; forming a mesa structure by etching the stacked semiconductor layer using a first mask, the mesa structure including a side surface and a bottom portion of the first core layer; forming a protective mask covering the side surface; etching the bottom portion using the protective mask to form a top mesa; and forming a bottom mesa by etching the second core layer using a second mask. The top mesa includes the first core layer and a portion having a mesa width gradually reduced in a first direction of a waveguide axis. The bottom mesa includes the second core layer and a portion having a mesa width gradually reduced in a second direction opposite to the first direction.

Abstract: A method for producing a semiconductor optical device includes the steps of forming first and second optical waveguides; forming a first resin layer on the first and the second optical waveguides; forming an opening in the first resin layer; forming a first electrode in the opening; forming a second resin layer on the first electrode and the first resin layer; forming a groove in the second resin layer on the first electrode; forming a second electrode on the second resin layer, a side surface of the groove, and the top surface of the first electrode; and forming a third electrode on the second electrode. The second and third electrodes have a region in which the second and third electrodes pass over the second optical waveguide, and, in the region, the first and second resin layers are disposed between the second electrode and the second optical waveguide.

Abstract: A method for manufacturing a Mach-Zehnder modulator includes the steps of forming a stacked semiconductor layer, the stacked semiconductor layer including a first conductivity type semiconductor layer, a core layer and a second conductivity type semiconductor layer, forming a waveguide mesa, the waveguide mesa having a first portion, a second portion and a third portion arranged between the first and second portions; forming a buried region on the waveguide mesa; forming an opening in the buried region on the third portion by etching the buried region using a mask; etching the second conductivity type semiconductor layer in the third portion through the buried region as a mask; and removing the buried region after etching the second conductivity type semiconductor layer. In the step of etching the second conductivity type semiconductor layer, the buried region covers a side surface of the third portion of the waveguide mesa.

Abstract: A method for manufacturing a semiconductor modulator includes the steps of preparing a substrate having a main surface including first and second areas; forming a stacked semiconductor layer on the main surface; forming an optical waveguide mesa by etching the stacked semiconductor layer using a mask, the optical waveguide mesa including an optical modulation portion; applying a resin on a top surface and a side surface of the optical waveguide mesa and on the substrate; forming a first opening in the resin on the second area of the substrate; forming an underlayer structure on the second area of the substrate in contact with the substrate; and forming a pad electrode on the underlayer structure in contact with the underlayer structure through the first opening of the resin. The underlayer structure includes an insulating layer made of a dielectric material.

Abstract: A semiconductor optical waveguide device includes a substrate having a first area and a second area, and first, second, and semiconductor mesas on the substrate. The first semiconductor mesa includes a cladding layer and a first mesa portion on the second area, the first mesa portion including first and second portions. The second semiconductor mesa includes an intermediate layer, a first core layer, and first and second mesa portions on the first and second area, respectively. The third semiconductor mesa includes a second core layer, and first and second mesa portions having a greater width than that of the second semiconductor mesa. The first portion of the first semiconductor mesa has a substantially the same width as the second mesa portion of the second semiconductor mesa. The first core layer is optically coupled to the second core layer through the intermediate layer disposed between the first and second core layers.

Abstract: A semiconductor device includes a Si substrate having a principal plane that is a crystal surface inclined at an off angle of 0.1 degrees or less with respect to a (111) plane, an AlN layer that is provided so as to contact the principal plane of the Si substrate and is configured so that an FWHM of a rocking curve of a (002) plane by x-ray diffraction is not greater than 2000 seconds, and a GaN-based semiconductor layer formed on the AlN layer.

Abstract: A method for producing an optical semiconductor device includes the steps of determining a wafer size to make a section arrangement including a plurality of sections in each of which the optical semiconductor device including a semiconductor mesa is formed; obtaining an in-plane distribution of a thickness of a resin layer on a wafer; obtaining a correlation between a thickness of a resin layer and a trench width; forming a trench width map using the in-plane distribution of the thickness and the correlation; preparing an epitaxial substrate by forming a stacked semiconductor layer; forming, on the epitaxial substrate, a mask based on the trench width map; forming a trench structure including the semiconductor mesa by etching the stacked semiconductor layer using the mask; forming a resin layer on the trench structure; and forming an opening on the semiconductor mesa by etching the resin layer.