Vertical insulated gate transistor and manufacturing method

A semiconductor device, comprising:

• a semiconductor body having opposed first and second major surfaces, the semiconductor body having a highly doped drain layer of a first conductivity type and lower doped body layer on the highly doped layer facing the first major surface;
• a trench extending into the semiconductor body from the first major surface defining opposed sidewalls and a base;
• a source region of the first conductivity type laterally adjacent to the trench at the first major surface;
• a gate dielectric on the sidewalls and base of the trench;
• opposed gate elements on the sidewalls of the trench but not on the base of the trench;
• an insulating filler extending upwards from the base of the trench between the gate elements;
• and
• a gate electrical connection layer at the top of the trench above the insulating filler, the gate electrical connection layer connecting the gate elements across the trench.