Patent ID: 7339237

Claim:
A power transistor, having a semiconductor volume comprising: a plurality of transistor cells connected in parallel; a laterally oriented, highly conductive semiconductor layer buried below the transistor cells in the semiconductor volume; and at least one connection, via which the buried semiconductor layer can be contact-connected from a top side of the power transistor; wherein at least one connection is formed within a trench extending from the top side of the power transistor towards the buried semiconductor layer; wherein the buried semiconductor layer is surrounded by an insulation ring made of semiconductor material or is embedded in an insulation semiconductor layer; wherein one of the insulation ring and the outer edge of the insulation semiconductor layer in which the buried semiconductor layer is embedded constitutes a vertical lengthening of a trench ring extending from the top side of the power transistor in to the depth of the semiconductor volume; and wherein the trench bottom of the trench ring is lined with a highly conductor layer.