Vertical DMOS transistor

A transistor, comprising:

• a semiconductor body of a first conductivity type;
• a first gate electrode formed on a first portion of the semiconductor body and insulated from the semiconductor body by a gate dielectric layer, a drain region of a second conductivity type formed on a first side of the first gate electrode and a first source region of the second conductivity type formed on a second side of the first gate electrode, the second side opposite the first side;
• a second gate electrode formed on a second portion of the semiconductor body and insulated from the semiconductor body by the gate dielectric layer, the drain region being formed on a first side of the second gate electrode and a second source region of the second conductivity type formed on a second side of the second gate electrode;
• a trench formed in the semiconductor body and positioned in the drain region, the trench being lined with a thin dielectric layer as a sidewall dielectric layer;
• a doped sidewall region of the second conductivity type formed in the semiconductor body along the sidewall of the trench outside of the trench, the doped sidewall region being in electrical contact with the drain region and forming a vertical drain current path for the transistor, the drain current of the transistor flowing in the doped sidewall region in the semiconductor body outside of the trench;
• a trench bottom doped region of the second conductivity type formed in the semiconductor body beneath the trench and in electrical contact with the doped sidewall region formed in the semiconductor body along the sidewall of the trench,
• wherein the trench is filled at an outer perimeter with a bottom dielectric layer at a lower portion of the trench and a first conductive layer above the bottom dielectric layer, and the remaining portion of the trench is filled with a second conductive layer in electrical contact with the trench bottom doped region, the second conductive layer being electrically insulated from the first conductive layer by a dielectric layer, the second conductive layer forming a trench drain electrode, the drain current of the transistor flowing in the vertical drain current path is directed to the trench bottom doped region and to the trench drain electrode.