An electrode contact structure having a high reliability is provided. The structure comprises an Au electrode formed on a GaAs substrate, a contact hole open in an insulating film on the Au electrode, and an Al wiring being in contact with the Au electrode through the contact hole. The difference between the height of the portion having the maximum thickness of the Al wiring and the height of the portion having the minimum thickness of the Al wiring is substantially equal to or smaller than the thickness of the insulating film. It is preferable that the thickness of the Au electrode is in the range of 0.1-0.2 .mu.m, the overlapped width between the peripheral portion of the Au electrode and the insulating film is 1 .mu.m or less, or the area of the contact hole is at least 16 .mu.m.sup.2 or more.