Electrode structures, gallium nitride based semiconductor devices including the same and methods of manufacturing the same

A method of manufacturing a GaN-based semiconductor device, the method comprising:

• preparing a GaN-based semiconductor layer including a first region, a second region and a third region between the first region and the second region;
• forming an electrode structure on at least one of the first region and the second region of the GaN-based semiconductor layer,
• the forming an electrode structure comprising,
• forming a diffusion layer on the GaN-based semiconductor layer, the diffusion layer including a material which is an n-type dopant with respect to the GaN-based semiconductor layer, and the diffusion layer contacting at least one of the first region and the second region of the GaN-based semiconductor layer,
• forming an electrode element including a conductive material on the diffusion layer, and
• etching an upper surface of the at least one of the first region and the second region of the GaN-based semiconductor layer to form a first recess;
• forming a gate electrode on the GaN-based semiconductor layer;
• forming a gate insulation layer between the GaN-based semiconductor layer and the gate electrode;
• forming an etching barrier layer on the gate insulation layer, the etching barrier layer over only the third region of the GaN-based semiconductor layer;
• and
• annealing the diffusion layer and the GaN-based semiconductor layer so as to diffuse the n-type dopant of the diffusion layer into at least one of the first region and the second region of the GaN-based semiconductor layer.