An object of the invention is to provide a semiconductor device which has a capacitor having good anti-leak characteristics and good breakdown voltage characteristics and is suitable to high integration. Source/drain regions (25) are formed at a surface of a silicon substrate (31). Interlayer insulating films (1) and (3) having contact holes (1a) and (3a), through which a surfaces of the source/drain region is partially exposed, is formed on the surface of silicon substrate (31). Contact holes (1a) and (3a) are filled with plug layer (9a). A capacitor (20) having a highly dielectric film (15) is formed such that it is electrically connected to source/drain region (25) through plug layer (9a). The interlayer insulating film is formed of a two-layer structure including a silicon oxide film (1) and a silicon nitride film (3). Silicon nitride film (3) and plug layer (9a) have the top surfaces flush with each other.