Described herein is a gated bipolar
semiconductor device comprising a collector region (104) of a first
conductivity type, a drift region (106, 108) of a second
conductivity type over the collector region, a
body region (110) of the first
conductivity type over the drift region, a
body region (112) of the second conductivity type over the drift region, at least one first
contact region of a second conductivity type over the
body region and having a higher
doping concentration than the body region, at least one second
contact region (116) of the first conductivity type laterally adjacent to the at least one first
contact region, the at least one second contact region has a higher
doping concentration than the body region, at least one active trench (124) extending from the surface into the drift region wherein the at least one first contact region adjoins the at least one active trench such that, in use, a channel region is formed along the at least one active trench and within the body region, and at least two auxiliary trenches (118) extending from the surface into the drift region. The at least two auxiliary trenches each include an insulating layer (122) along the vertical sidewalls and the bottom surface. A thickness of the insulating layer along two vertical sidewalls of the at least two auxiliary trenches is less than 1500 A. The body region of the first conductivity type and the body region of the second conductivity type are both at least located between two adjacent auxiliary trenches. Possibly, the device further includes a
transmitter trench (336) located between the two active trenches (124) and recessed from the top surface.