hereinafter , a description is made on an embodiment of the present invention with reference to the drawings . fig1 is a plan view illustrating a structure of a semiconductor integrated circuit ( ic chip ) 1 according this embodiment . the semiconductor integrated circuit 1 according to this embodiment is formed on a chip substrate ( hereinafter , referred to as semiconductor substrate 2 ) which is obtained by dicing a wafer substrate . the semiconductor substrate 2 includes a plurality of i / o cells 3 arranged in an i / o region 21 in a chip peripheral portion , and an internal core region 4 including a plurality of logic cells ( not shown ) and a plurality of memory cells ( not shown ). on the i / o cells 3 or the internal core region 4 , a plurality of bonding pads are arranged . the plurality of bonding pads 5 are arranged along a first pad row 26 and a second pad row 27 . on the first pad row 26 , a plurality of bonding pads for signal 5 are formed . on the second pad row 27 , the plurality of bonding pads for signal 5 , at least one first bonding pad for power supply 6 , and at least one second bonding pad for power supply 7 are formed . a first power supply ring 8 and a second power supply ring 9 are formed on the internal core region 4 . the first power supply ring 8 is connected to the first bonding pad for power supply 6 . the second power supply ring 9 is connected to the second bonding pad for power supply 7 . circuit devices such as the logic cells and the memory cells arranged in the internal core region 4 operate in response to electric power supplied through the first power supply ring 8 and the second power supply ring 9 . fig2 is a plan view illustrating in detail the structure of the semiconductor integrated circuit 1 . as illustrated in fig2 , the bonding pads for signal 5 , the first bonding pad for power supply 6 , and the second bonding pad for power supply 7 are connected to the i / o cells 3 through connection contacts for signal 19 . the first bonding pad for power supply 6 is connected to the first power supply ring 8 through a first power supply ring connection wiring 15 . further , the first bonding pad for power supply 6 is connected to a first expansion power supply ring 11 through a first expansion ring connection contact 17 . the second bonding pad for power supply 7 is connected to the second power supply ring 9 through a second power supply ring connection wiring 16 . further , the second bonding pad for 5 power supply 7 is connected to a second expansion power supply ring 12 through a second expansion ring connection contact 18 . the internal core region 4 includes a primary core region 22 and an expansion core region 23 . a plurality of upper layer wirings 13 extending in a first direction are arranged on the primary core region 22 . moreover , on the primary core region 22 , a plurality of upper layer wirings 13 extending in a second direction orthogonal to the first direction are arranged . in the primary core region 22 , a plurality of lower layer wirings 14 are arranged below the upper layer wirings 13 . in the semiconductor integrated circuit 1 according to this embodiment , the expansion core region 23 includes the bonding pads for signal 5 , the first bonding pad for power supply 6 , and the second bonding pad for power supply 7 arranged therein , and the first expansion power supply ring 11 and the second expansion power supply ring 12 are arranged below the bonding pads for signal 5 , the first bonding pad for power supply 6 , and the second bonding pad for power supply 7 . further , in the expansion core region 23 , a plurality of lower layer wirings 14 are arranged below the first expansion power supply ring 11 or the second expansion power supply ring 12 . fig3 is a sectional view illustrating a cross section of the semiconductor integrated circuit 1 of this embodiment . fig3 illustrates a structure of the cross section of the semiconductor integrated circuit 1 cut at a position denoted by the line segment a - a of fig2 described above . as illustrated in fig3 , the semiconductor integrated circuit 1 includes the i / o cell 3 and the internal core region 4 which are formed on 5 the semiconductor substrate 2 . predetermined circuit devices ( not shown ) are formed on the i / o cell 3 and the internal core region 4 . in this embodiment , a description on the detailed structure of the circuit devices and illustration thereof in the drawings are omitted for the purpose of facilitating understanding of the present invention . referring to fig3 , the internal core region 4 is formed so as to correspond to the primary core region 22 and the expansion core region 23 . in the expansion core region 23 , the lower layer wirings 14 corresponding to a plurality of wiring layers are arranged above the internal core region 4 . further , the semiconductor integrated circuit 1 of this embodiment includes an upper layer wire mesh 24 and a lower layer wire mesh 25 . the plurality of upper layer wirings 13 are arranged in the upper layer wire mesh 24 . the plurality of upper layer wirings 13 are arranged in the respective wiring layers . further , the upper layer wire mesh 24 includes the first bonding pad for power supply 6 , the first power supply ring 8 , and the second power supply ring 9 arranged therein . the plurality of lower layer wirings 14 are arranged in the lower layer wire mesh 25 . the plurality of lower layer wirings 14 are arranged in the respective wiring layers . further , the lower layer wire mesh 25 includes the first expansion power supply ring 11 and the second expansion power supply ring 12 arranged therein . at the cross section of the line segment a - a , the first bonding pad for power supply 6 is connected to the first expansion power supply ring 11 through the first expansion ring connection contact 17 . further , the first bonding pad for 5 power supply 6 is connected to the first power supply ring 8 through the first power supply ring connection wiring 15 . fig4 is a sectional view illustrating a cross section of the semiconductor integrated circuit 1 of this embodiment . fig4 illustrates a structure of the cross section of the semiconductor integrated circuit 1 cut at a position denoted by the line segment b - b of fig2 described above . referring to fig4 , at the cross section of the line segment b - b , the second bonding pad for power supply 7 is connected to the second expansion power supply ring 12 through the second expansion ring connection contact 18 . further , the second bonding pad for power supply 7 is connected to the second power supply ring 9 through the second power supply ring connection wiring 16 . fig5 is a sectional view illustrating a cross section of the semiconductor integrated circuit 1 of this embodiment . fig5 illustrates a structure of the cross section of the semiconductor integrated circuit 1 cut at a position denoted by the line segment c - c of fig2 described above . referring to fig5 , at the cross section of the line segment c - c , the bonding pads for signal 5 are formed in the semiconductor integrated circuit 1 . the bonding pads for signal 5 are connected to the i / o cells 3 through the connection contacts for signal 19 . as described above , the primary core region 22 , the lower layer wirings 14 , and the plurality of bonding pads ( bonding pads for signal 5 , first bonding pad for power supply 6 , and second bonding pad for power supply 7 ) are formed in the semiconductor integrated circuit 1 of this embodiment . with 5 this structure , the internal core region 4 can be formed substantially below the bonding pads for signal 5 , the first bonding pad for power supply 6 , and the second bonding pad for power supply 7 , whereby the chip area can be utilized more efficiently . further , in the semiconductor integrated circuit 1 of this embodiment , the first expansion power supply ring 11 is connected to the first bonding pad for power supply 6 through the first expansion ring connection contact 17 , and the second expansion power supply ring 12 is connected to the second bonding pad for power supply 7 through the second expansion ring connection contact 18 . as described above , the first bonding pad for power supply 6 or the second bonding pad for power supply 7 is directly connected to the first expansion power supply ring 11 or the second expansion power supply ring 12 . accordingly , the first expansion power supply ring 11 or the second expansion power supply ring 12 can supply a power which is supplied from the first bonding pad for power supply 6 or the second bonding pad for power supply 7 , directly to the lower layer wirings 14 provided therebelow . with this structure , power supply performance can be increased with respect to the circuit devices provided in the primary core region 22 .