Semiconductor device and method for making the same

A method for making a semiconductor device comprising:

• forming a narrower trench and a wider trench with different widths on the same surface of a semiconductor substrate;
• burying the inside of the narrower trench with film material through deposition of the film on a surface in the semiconductor substrate where the narrower trench and the wider trench are formed, whereas forming a film with a certain film thickness in the wider trench;
• and
• performing etching in the semiconductor substrate for leaving some portions of the film in the narrower trench and for removing film material in the wider trench.

A method for making the semiconductor device comprising:

• concurrently forming a first trench, a second trench wider than the first trench, and a third trench wider than the second trench on the same surface of a semiconductor layer;
• forming an oxide film on a surface of the semiconductor layer;
• filling up the first trench with conductive material without filling up the second trench and the third trench therewith, through deposition of the conductive material on the semiconductor layer where the oxide film is formed, the conductive material corresponding to a gate electrode;
• removing by etching the conductive material deposited in the second trench and the third trench with the conductive material being left in the first trench;
• filling up the second trench with insulating material without filling up the third trench therewith, through deposition of the insulating material on the semiconductor layer where the oxide film is formed, the insulating material corresponding to an embedded insulation layer;
• removing by etching the insulating material and the oxide film deposited in the third trench with the insulating material being left in the second trench;
• and
• covering at least an inner surface of the third trench with metallic material, through deposition of the metallic material on the semiconductor layer, the metallic material corresponding to an electrode film.