Semiconductor device and method of manufacturing the same

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

• forming a concave portion, a trench source portion, and a trench drain portion by etching in a vicinity of a first conductivity type surface of a semiconductor substrate, the concave portion being varied in depth along a gate width direction, the trench source portion and the trench drain portion being embedded with polycrystalline silicon that contains an impurity to form a source region and a drain region;
• forming an insulating film on a surface of the semiconductor substrate including inner walls of the concave portion, the trench source portion, and the trench drain portion;
• filling, after removing the insulating film from the inner walls of the trench source portion and the trench drain portion, insides of the concave portion, the trench source portion, and the trench drain portion with polycrystalline silicon that contains a high concentration of a second conductivity type impurity;
• and
• diffusing the second conductivity type impurity from the polycrystalline silicon that fills the trench source portion and the trench drain portion to form the source region and the drain region.

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

• forming a concave portion, a trench source portion, and a trench drain portion by etching in a vicinity of a first conductivity type surface of a semiconductor substrate, the concave portion being varied in depth along a gate width direction, the trench source portion and the trench drain portion being embedded with polycrystalline silicon that contains an impurity to form a source region and a drain region;
• forming an insulating film on a surface of the semiconductor substrate including inner walls of the concave portion, the trench source portion, and the trench drain portion;
• filling an inside of the concave portion with polycrystalline silicon;
• filling, after covering the polycrystalline silicon that fills the inside of the concave portion with an oxide film, and after removing the insulating film from the inner walls of the trench source portion and the trench drain portion, insides of the trench source portion and the trench drain portion with polycrystalline silicon that contains a high concentration of a second conductivity type impurity;
• and
• diffusing the second conductivity type impurity from the polycrystalline silicon that fills the trench source portion and the trench drain portion to form the source region and the drain region.