Semiconductor device and method of manufacturing the same

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

• forming an insulating layer on a front surface of a semiconductor substrate, a second region of a second conductivity type in a surface area of the semiconductor substrate, and a field insulating layer in a surface area of the second region;
• forming a resist film having a pattern including an opening portion corresponding to a part of the field insulating layer;
• removing an upper portion of a part of the field insulating layer by using the resist film as a mask;
• forming a gate electrode in a way that a part of a gate insulating layer formed on the front surface of the semiconductor substrate and a part of the field insulating layer including a step are covered with the gate electrode;
• forming a first region of a first conductivity type in a surface area of the semiconductor substrate;
• and
• forming a source region of the second conductivity type in a surface area of the first region, and a drain region of the second conductivity type in a surface area of the second region.

A method for manufacturing a semiconductor device comprising the step of:

• forming
• a first insulating layer on a front surface of a first formation section of a semiconductor substrate, and a second insulating layer on a front surface of a second formation section of the semiconductor substrate,
• a second region of a second conductivity type in a surface area of the first formation section, and a fourth region of the second conductivity type in a surface area of the second formation section, and
• a first field insulating layer in a surface area of the second region, and a second field insulating layer in a surface area of the fourth region,
• forming a step by removing a part of the first insulating layer and an upper portion of a part of the first field insulating layer in the first formation section;
• forming, by thermal oxidation, a first gate insulating layer on a front surface of the resultant first formation section, and a second gate insulating layer on a front surface of the resultant second formation section, the second gate insulating layer being obtained by thickening the second insulating layer;
• forming a first gate electrode in a way that a part of the first gate insulating layer and a part of the first field insulating layer including the step are covered with the first gate electrode, while forming a second gate electrode in a way that a part of the second gate insulating layer and a part of the second field insulating layer are covered with the second gate electrode;
• forming a first region of a first conductivity type in a surface area of the consequent first formation section, and a third region of the first conductivity type in a surface area of the consequent second formation section;
• and
• forming a first source region of the second conductivity type in a surface area of the first region, and a first drain region of the second conductivity type in a surface area of the second region, while forming a second source region of the second conductivity type in a surface area of the third region, and a second drain region of the second conductivity type in a surface area of the fourth region.