Provided is a semiconductor device comprising: an HSQ layer formed on a Cu wiring line and having properties that Cu is unlikely to enter the HSQ layer; a plug formed in the HSQ layer and connected to the Cu wiring line; and a Cu wiring line inserted inside the HSQ layer and connected to the plug. A W layer which allows the plug and the HSQ layer to adhere to each other is formed between the plug and the HSQ layer, and another W layer which allows the Cu wiring line and the HSQ layer to adhere to each other and which is formed of tungsten is formed between the Cu wiring line and the HSQ layer.