An electrode structure on a p-type III group nitride semiconductor layer includes
first, second and third electrode layers successively stacked on the semiconductor
layer. The first electrode layer includes at least one selected from a first metal
group of Ti, Hf, Zr, V, Nb, Ta, Cr, W and Sc. The second electrode layer includes
at least one selected from a second metal group of Ni, Pd and Co. The third electrode
layer includes Au.
