Abstract: Provided is a semiconductor device capable of reducing switching loss at turn-off while suppressing conduction loss. An emitter p? layer 11, a collector p layer 23, a drift layer 10, an emitter electrode 18, a collector electrode 28, an emitter-side gate electrode 17, an emitter n layer 12, a collector p? layer 23a, a collector-side gate electrode 27, and a collector n layer 22 configure a semiconductor device 1, and a total length of a first facing region of the emitter-side gate electrode 17 in a gate width direction facing an emitter layer p? 11 via a gate insulating film 15 is longer than the total length in the gate width direction of a second facing region of a collector-side gate electrode 27 facing an impurity layer 23a via a collector-side gate insulating film 25.

Abstract: A holding chuck has a clamping device for firmly holding the tire-wheel in the position aligned with a center axis of a holding chuck. Chatter-suppressing dampers are disposed on an intermediate plate fitted around the chuck. The dampers are disposed on circles concentric with the center axis of the holding chuck. Each of the dampers has a damping rod extending in the direction parallel to the center axis and abutting a rim of the wheel. A damper cover is disposed between the rim of the wheel and the dampers and fastened to the holding chuck. The damper cover has slot holes disposed on a circle concentric with the center axis of the chuck which allow the damping rods of the dampers disposed on only one of the concentric circles to extend therethrough and abut the rim of the wheel.