and housing a first connection line 6 connected to the surface 5 a of the first insulating layer 5 through a first via 7 and a first contact pad 8 a first metal region 9 extends on top of the surface 5 a of the first insulating layer 5 overlies and is in direct electrical contact with the first contact pad 8 the second wafer 3 comprises a second insulating layer 13 having a surface 13 a and housing a second connection line 14 connected to the surface 13 a of the second insulating layer 13 through a second via 15 and a second contact pad 16 a second metal region 19 extends on top of the surface 13 a of the second insulating layer 13 overlies and is in direct electrical contact with the second contact pad 16 in addition a plug region 20 and spacing regions 21 extend on top of the surface 13 a of the second insulating layer 13 in detail the plug region 20 is formed on top of and in direct electrical contact with the second metal region 19 and has a greater height than that of the spacing regions 21 the plug region 20 has the purpose of electrically connecting the first metal region 9 and the second metal region 19 and must reflow when bonding the two wafers 2 3 for this purpose the material of the plug region 20 must be able to.