Semiconductor device having non-planar interface between a plug layer and a contact layer

A semiconductor device is provided, in which it becomes easy to reliably couple a plug conductive layer and a wiring layer located over the plug conductive layer to each other and falling of the wiring can be suppressed. The plug conductive layer contacts a source/drain region formed over a major surface of the semiconductor substrate. A contact conductive layer is formed so as to contact both the upper surface and the side surface of the plug conductive layer. Wiring layers are formed over the contact conductive layer so as to be electrically coupled to the contact conductive layer.