Patent ID: 8222672

Claim:
A semiconductor device comprising: a substrate; an n-type nitride semiconductor layer or an undoped nitride semiconductor layer over the substrate; and a source electrode and a drain electrode being in direct physical contact with and being in ohmic contact with said n-type nitride semiconductor layer or said undoped nitride semiconductor layer; wherein each of said source electrode and said drain electrode comprises: a tantalum layer formed on said n-type nitride semiconductor layer or said undoped nitride semiconductor layer; an aluminum layer formed on said tantalum layer and made of aluminum only; and a metal layer formed on said aluminum layer and made of any one material of tantalum, nickel and palladium; further comprising a compound layer of aluminum and any one material of tantalum, nickel and palladium between said aluminum layer and said metal layer; and a gate electrode comprising a nickel layer and a gold layer formed on the nickel layer.