Semiconductor device and method of manufacturing the same

A method of manufacturing a semiconductor device, comprising:

• forming a first conductivity type lower well region on a semiconductor substrate;
• forming a second conductivity type lower low-concentration region in a part of the first conductivity type lower well region;
• forming a second conductivity type lower source region and a second conductivity type lower drain region in a part of the lower low-concentration region, the second conductivity type lower source region and the second conductivity type lower drain region having higher impurity concentration than lower low-concentration region;
• forming a semiconductor epitaxial layer on a substrate surface of the first conductivity type lower well region, a substrate surface of the second conductivity type lower source region, and a substrate surface of the second conductivity type lower drain region;
• forming an upper well region on the semiconductor epitaxial layer;
• etching the semiconductor substrate to form a trench having a depth deeper than a depth of the lower source region and the lower drain region and forming a convex-concave portion;
• forming an insulating film on an entire surface of the convex-concave portion, and forming a gate electrode via the insulating film;
• performing ion implantation on both sides of the gate electrode and forming a second conductivity type upper low-concentration region in contact with the lower source region and the lower drain region, respectively;
• and
• forming a second conductivity type upper source region and a second conductivity type upper drain region on a source side of the gate electrode and on a part of a drain side of the gate electrode, the second conductivity type upper source region and the second conductivity type upper drain region having higher impurity concentration than the second conductivity type upper low-concentration region.