Transistor structures gated using a conductor-filled via or trench

A method of forming a device structure using a substrate, the method comprising:

• forming a doped region in the substrate;
• forming an opening in the substrate that extends through the doped region and into a portion of the substrate beneath the doped region;
• forming a dielectric layer on the substrate inside the opening;
• and
• forming a conductive plug inside the opening,
• wherein the doped region has an opposite conductivity type from the portion of the substrate, the dielectric layer is located in the opening between the conductive plug and the substrate, and the opening is positioned and dimensioned relative to a position and dimensions of the doped region to divide the doped region into a first section and a second section that is disconnected from the first section by the opening.