An electrode pad for a Group III nitride compound semiconductor having
p-type conduction includes a triple layer structure having first, second,
and third metal layers, formed on an electrode layer. A protection film
with a window exposing a central portion of the third metal layer is
formed by etching on the third metal layer and covers the sides of the
first, second, and third metal layers. The second metal layer is made of
gold (Au). The first metal layer is made of an element which has
ionization potential lower than gold (Au). The third metal is made of an
element which has adhesiveness to the protection film stronger than that
of gold (Au). Consequently, this structure of the electrode pad improves
the adhesive strength between the protection layer and the third meal
layer and prevents the etching of the sides of the protection film.
Furthermore, the contact resistance between the semiconductor and the
electrode pad is lowered and, thus, ohmic characteristic of the electrode
pad is improved.
