With a stopper layer 19 as an etching stopper, a second groove 14a and a contact hole 13a are formed. Copper is buried inside the second groove 14a and the contact hole 13a, thereby forming a plug layer 22 and an overlying wiring layer 21 connected to an underlying wiring layer 17 via the plug layer...http://www.google.com/patents/US6949829?utm_source=gb-gplus-sharePatent US6949829 - Semiconductor device and fabrication method therefor
