Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a semiconductor substrate;
• an active element structure formed on the semiconductor substrate, and having a connection region formed in a surface of the semiconductor substrate;
• an insulating film formed on the semiconductor substrate;
• a connection hole formed in the insulating film, having a bottom connected with the connection region, and including a first region and a second region formed over the first region;
• an interconnect trench formed in the insulating film, and having a bottom connected with the connection hole;
• a first conductive film filled in the first region of the connection hole, and consisting of an alloy containing CoW or NiW;
• a second conductive film filled in the interconnect trench and the second region of the connection hole, and contacting with the first conductive film;
• and
• a first diffusion prevention film formed between an inner surface of the interconnect trench and the second conductive film, between a side surface of the connection hole in the second region and the second conductive film and on the first conductive film.