Semiconductor device and method of manufacturing the same

A method of manufacturing a semiconductor device comprising the steps of:

• partitioning a semiconductor substrate into a plurality of device regions by forming device isolation regions on the semiconductor substrate;
• forming a first insulating film on at least the device regions;
• forming a plurality of conductive layers to pass over the device isolation regions and the device regions;
• forming impurity diffusion regions by introducing impurity into the semiconductor substrate on both sides of the conductive layers in the device regions;
• covering peripheral regions of the conductive layers with a second insulating film;
• forming a third insulating film on an overall upper surface of the semiconductor substrate containing the second insulating film;
• forming opening portions in the third insulating film to extend over the plurality of device regions and to reach the impurity diffusion regions respectively;
• forming a conductive film to bury the opening portions by depositing conductor on the semiconductor substrate containing the third insulating film;
• and
• removing the third insulating film and the conductive film until at least one of the second insulating film over the device isolation regions and the second insulating film over the device regions is exposed, to isolate electrically mutually the conductor buried in the opening portions, whereby contact plugs are formed.