In an electrode structure for a nitride III-V compound semiconductor device, a metallic nitride
is used as an electrode material. A metallic material of the metallic nitride has a negative
nitride formation free energy, and comprises at least one metal selected from a group
consisting of IVa-group metals such as titanium and zirconium, Va-group metals such as
vanadium, niobium, and tantalum, and VIa-group metals such as chromium, molybdenum,
and tungsten.