Breakdown voltage improvement in vertical trench-gate devices

A vertical transistor comprising:

• a semiconductor region of a first conductivity type;
• a plurality of perpendicularly intersecting trenches having a shielded gate structure of the vertical transistor disposed therein;
• and
• a mesa of the semiconductor region defined by the plurality of perpendicularly intersecting trenches, the mesa including:
• a first end portion having a first width;
• a second end portion having a second width;
• and
• a central portion disposed between the first end portion and the second end portion, the central portion having a third width that is greater than the first width and the second width.

A method for producing a vertical transistor, the method comprising:

• defining a mesa in a semiconductor region of a conductivity type by forming a plurality of intersecting trenches in the semiconductor region, the mesa including:
• a first end portion having a first width;
• a second end portion having a second width;
• and
• a central portion disposed between the first end portion and the second end portion, the central portion having a third width that is greater than the first width and the second width.