Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a semiconductor substrate having an upper surface;
• a first trench electrode placed inside a first trench formed on the upper surface;
• a second trench electrode placed inside a second trench formed on the upper surface;
• a third trench electrode placed inside a third trench formed on the upper surface;
• a first trench insulating film placed between the first trench electrode and the semiconductor substrate;
• a second trench insulating film placed between the second trench electrode and the semiconductor substrate;
• and
• a third trench insulating film placed between the third trench electrode and the semiconductor substrate,
• wherein the semiconductor substrate includes:
• a first semiconductor layer of a first conductivity type,
• a floating layer of a second conductivity type placed on the first semiconductor layer, a lower end of each of the first, second and third trench electrodes reaching the floating layer,
• a barrier layer of the first conductivity type placed on the floating layer and being in contact with the first, second and third trench insulating films,
• a second semiconductor layer of the second conductivity type placed on the barrier layer and being in contact with the first, second and third trench insulating films, and
• a third semiconductor layer of the first conductivity type placed on the second semiconductor layer,
• wherein the third semiconductor layer, the second semiconductor layer and the barrier layer are separated from the first semiconductor layer by the floating layer,
• wherein a path of a carrier passing through an inverted layer formed in the second semiconductor layer includes the second semiconductor layer, the barrier layer, a non-inverted region of the floating layer, and the first semiconductor layer,
• wherein a gate voltage is applied to the first trench electrode for forming an inverted region in a part of the second semiconductor layer in contact with the trench insulating film,
• wherein an emitter voltage is applied to the second and third trench electrodes for establishing continuity between the first semiconductor layer and the third semiconductor layer, and
• wherein the lower end of each of the first, second and third trench electrodes is covered with the floating layer via each of the first, second and third trench insulating films such that the first, second and third trench insulating films are directly in contact with the floating layer.