Method for manufacturing a semiconductor device

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

• preparing a semiconductor substrate having a projection at a first part;
• forming a first protection film on said projection with an oxide film interposed therebetween;
• forming a buried insulation film covering said substrate and said first protection film;
• forming a second protection film at a level higher than a top surface of said first protection film and on that part of said buried insulation film which is located above a part of said substrate which is other than said first part;
• polishing said buried insulation film by chemical mechanical polishing using said second protection film as a stopper, thereby easing irregularities of a polished surface of said buried insulation film;
• and
• removing said second protection film;
• polishing said buried insulation film by chemical mechanical polishing using said first protection film as a stopper, thereby flattening a polished surface of said buried insulation film.

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

• preparing a semiconductor substrate having a projection at a first part;
• forming a first protection film on a top surface of said projection;
• forming a buried insulation film covering said substrate and said first protection film;
• forming a second protection film at a level higher than a top surface of said first protection film and on that part of said buried insulation film which is located above a part of said substrate which is other than said first part;
• polishing said buried insulation film by chemical mechanical polishing using said second protection film as a stopper, thereby easing irregularities of a polished surface of said buried insulation film;
• and
• removing said second protection film;
• polishing said buried insulation film by chemical mechanical polishing using said first protection film as a stopper, thereby flattening a polished surface of said buried insulation film;
• wherein said second protection film includes a carbon film.