to reinforce power supply wirings without sacrificing the interconnectivity of semiconductor devices . when three wirings are formed in parallel in the same wiring layer and the center wiring among them is shorter than the outer wirings , a projecting portion integrated into the outer wiring is formed utilizing a free space remaining on the extension of the center wiring . for example , when the outer wirings are used as power supply wirings , the power supply wirings can be reinforced by adding the projecting portion . at this time , because the projecting portion is arranged in the free space , the interconnectivity is not sacrificed .