A waveguide optical semiconductor device, a method of fabricating the same and an optical device module. The semiconductor device includes a substrate, a waveguide formed on the substrate, an electrode layer formed on the waveguide, and bumpers formed on the substrate. The bumpers are disposed on both side of the waveguide, and top surfaces of the bumpers are higher than a top surface of the electrode layer. The method of fabrication includes forming semiconductor layers for waveguide on a substrate, forming another semiconductor layer on the semiconductor layers, removing the another semiconductor layer and at least a part of the semiconductor layers selectively so that grooves are formed on both side of a region where the waveguide are expected to be formed, removing the another semiconductor layer at the region, remained portions of the another semiconductor layer form bumpers. The module includes a waveguide optical semiconductor device having bumpers disposed on both side of the waveguide, and a carrier having a mounting region in contact with the top surfaces of the bumpers.