A novel diode-clamped carrier stored trench bipolar transistor (CSTBT) with improved performances is proposed. The improvement has been achieved by introducing a P-layer region under the trench gate, which is connected to the cathode electrode through two integrated series diodes. In the blocking-state, almost all of the reverse voltage is sustained by Player/N-drift junction, which makes the doping concentration of the carrier stored layer is independent of the breakdown voltage,thus overcoming