Method for producing a trench transistor and trench transistor

An integrated circuit including a transistor comprising:

• a trench in a semiconductor substrate of a first conduction type;
• the trench being filled with a conductive filling, the conductive filling being insulated from the substrate by a gate dielectric;
• first source and drain regions in the surface of the substrate alongside the trench;
• second source and drain regions in the substrate;
• the second source and drain regions being disposed below the first source and drain regions, respectively, and, proceeding from the trench, having a smaller lateral extent than the first source and drain regions;
• an insulation spacer being disposed in an upper portion of the trench, the insulation spacer having a larger thickness than the gate dielectric.

An integrated circuit including a transistor comprising:

• a trench in a semiconductor substrate of a first conduction type;
• first source and drain regions in the surface of the substrate alongside the trench;
• a first conductive filling in the trench as a gate electrode the first conductive filling being insulated from the semiconductor substrate by a gate dielectric;
• the first conductive filling being disposed in a lower portion of the trench below the first source and drain regions;
• second source and drain regions in the substrate;
• the second source and drain regions being disposed below the first source and drain regions and, proceeding from the trench, having a smaller lateral extent than the first source and drain regions;
• an insulation spacer above the first conductive filling in the trench the insulation spacer having a larger thickness than the gate dielectric;
• and
• a second conductive filling an upper portion of the trench;
• the second conductive filling being in electric contact with the first conductive filling and being electrically insulated from the first and second source and drain regions by the insulation spacer.