We disclose herein a gate controlled bipolar semiconductor device comprising: a collector region of a first conductivity type; a drift region of a second conductivity type located over the collector region; a body region of a first conductivity type located over the drift region; a plurality of first contact regions of a second conductivity type located above the body region and having a higher doping concentration than the body region; a second contact region of a first conductivity type located laterally adjacent to the plurality of first contact regions, the second contact region having a higher doping concentration than the body region; at least two active trenches each extending from a surface into the drift region; an emitter trench extending from the surface into the drift region; wherein each first contact region adjoins an active trench so that, in use, a channel is formed along said each active trench and within the body region; wherein the second contact region adjoins the emitter trench; and wherein the emitter trench is located between two active trenches.