A semiconductor device with improved the adhesion between bonding pads and ball portions of gold wires is provided to improve the reliability of a semiconductor device. About 1 wt. % of Pd is contained in gold wires for connection between electrode pads formed on a wiring substrate and electrode pads (exposed areas of a top layer wiring formed mainly of Al) formed on a semiconductor chip. In bonded portions between the electrode and ball portions of the gold wires, an interdiffusion of Au and Al is suppressed to prevent the formation of Au.sub.4Al after PCT (Pressure Cooker Test). Thus, a desired bonding strength is obtained even when the pitch of the electrode pads is smaller than 65 .mu.m and the diameter of the ball portion is smaller than 55 .mu.m or the diameter of the wire portion of each gold wire is not larger than 25 .mu.m.