Transistor devices with extended drain regions located in trench sidewalls

A method for forming a transistor device comprising:

• forming a trench in a semiconductor material, the trench including a first vertical component sidewall of the semiconductor material and a second vertical component sidewall of the semiconductor material opposite the first vertical component sidewall, the trench including a bottom portion of the semiconductor material;
• implanting dopants of a first conductivity type for an extended drain region of the transistor device through an opening in a mask into the first vertical component sidewall, into the second vertical component sidewall, and into the bottom portion, wherein the implanting dopants is performed with an angled ion implantation process, wherein the mask is located over the semiconductor material and the opening corresponds to a location of the trench;
• implanting dopants of a second conductivity type through the opening into the bottom portion of the trench, wherein the second conductivity type is opposite the first conductivity type;
• removing the mask;
• forming a source region for the transistor device of the first conductivity type;
• forming a drain region for the transistor device of the first conductivity type, wherein the trench is located laterally between the source region and the drain region;
• forming a channel region of dopants of the second conductivity type in a portion of the first vertical component sidewall below the source region;
• forming a control terminal structure for the transistor device including a portion located in the trench;
• wherein the bottom portion of the trench has a net first conductivity type concentration after the implanting dopants of a first conductivity type, the implanting dopants of the second conductivity type, and the formation of the source region, the drain region, and the control terminal structure.