Transistor with Field Electrodes and Improved Avalanche Breakdown Behavior

A method for forming a transistor device comprising at least one transistor cell, the method comprising:

• forming in a semiconductor body in a drift region of a transistor cell an avalanche region, the avalanche region having a higher doping concentration than sections of the drift region adjacent the avalanche region, the avalanche region being spaced apart, in a direction perpendicular to a current flow direction of the transistor device, from a field electrode dielectric dielectrically insulating a field electrode from the drift region and, the avalanche region being spaced apart in the current flow direction of the transistor device from a pn junction between a body region and the drift region, the avalanche region including at least one section that is closer to a bottom plane than to a surface of the semiconductor body;
• and
• arranging the field electrode in a trench having a bottom in the bottom plane,
• wherein forming the avalanche region comprises forming a trench in the semiconductor body, implanting dopant atoms via a bottom of the trench into the drift region, and annealing at least those regions of the drift region into which the dopant atoms have been implanted.

A method for forming a transistor device comprising at least one transistor cell, the method comprising:

• forming in a semiconductor body in a drift region of the transistor cell an avalanche region which has a higher doping concentration than sections of the drift region adjacent the avalanche region,
• wherein forming the avalanche region comprises forming the avalanche region such that the avalanche region is spaced apart, in a direction perpendicular to a current flow direction, from a field electrode dielectric dielectrically insulating a field electrode from the drift region and, in the current flow direction, from a pn junction between a body region and the drift region, and that the avalanche region includes at least one section that is closer to a bottom plane than to a surface of the semiconductor body,
• wherein the field electrode is arranged in a trench having a bottom in the bottom plane
• and wherein forming the avalanche region comprises implanting non-doping particles into the drift region, and annealing at least those regions of the drift region into which the non-doping particles have been implanted.