Insulated gate bipolar transistor with reverse conducting current

An insulated gate bipolar transistor with a reverse conducting function comprising:

• a first semiconductor layer of a first conduction type;
• a second semiconductor layer of a second conduction type formed in contact with the first semiconductor layer at a bottom surface therebetween;
• a third semiconductor region of the first conduction type formed in the second semiconductor layer and having a junction portion extending to a top surface of said second semiconductor layer;
• a fourth semiconductor region of the second conduction type formed in the third semiconductor region and having a junction portion extending to said top surface of said second semiconductor layer;
• an insulated gate electrode formed at least over the third semiconductor region junction portion laterally extending between the fourth semiconductor region junction portion and a non-diffused potion of said second semiconductor layer which extends to the top surface thereof;
• a source electrode in contact with both the third semiconductor region and the fourth semiconductor region;
• a drain electrode for supplying a drain current through the first semiconductor layer;
• a fifth semiconductor region of the second conduction type which is electrically connected to the drain electrode via an external conductor, and formed within the second semiconductor layer having a junction portion extending to said top surface of the second semiconductor layer so as to pass therethrough a reverse conducting current opposite in direction to the drain current;
• a sixth semiconductor region of the second conduction type formed partially at or near the bottom surface between the first semiconductor layer and the second semiconductor layer, said sixth semiconductor region having an impurity concentration higher than that of the second semiconductor layer and formed into a given pattern to reduce an electric resistance on carriers passing between the fifth semiconductor region and a portion of the second semiconductor layer at a distance from the fifth semiconductor region, said sixth semiconductor region allowing the carriers to pass across the bottom surface between the first semiconductor layer and the second semiconductor layer;
• and
• an electrically isolated high-voltage withstand region provided between said fifth semiconductor region and an element region, said element region including at least said second semiconductor layer, said third semiconductor region and said fourth semiconductor region, said high-voltage withstand region providing a high voltage withstand barrier against high voltages produced in an end area of said element region,
• said sixth semiconductor region being provided below at least said element region and said high-voltage withstand region, and said given pattern of said sixth semiconductor region being such that at least a part of said sixth semiconductor region extends continuously from a portion below said element region to a portion below said high-voltage withstand region.

An insulated gate bipolar transistor with a reverse conducting function comprising:

• a first semiconductor layer of a first conductivity type;
• a second semiconductor layer of a second conductivity type which is in contact with the first semiconductor layer;
• a third semiconductor region of the first conductivity type which is formed in the second semiconductor layer such that junction portion thereof terminates at a surface of the second semiconductor layer;
• a fourth semiconductor region of the second conductivity type which is formed in the third semiconductor region such that junction portion thereof terminates at a surface of the third semiconductor region;
• a gate electrode formed on at least a channel region defined in the surface of the third semiconductor region between the second semiconductor layer and the fourth semiconductor region with a gate insulating film interposed therebetween;
• a source electrode contacting with both the third semiconductor region and the fourth semiconductor region;
• a drain electrode for supply of a drain current through the first semiconductor layer;
• a fifth semiconductor region of the second conductivity type which is electrically connected to the drain electrode and formed in a given surface region within the second semiconductor layer, so as to pass therethrough a reverse conducting current opposite in direction to the drain current;
• a high-voltage withstand region for ensuring a high withstand voltage provided between the fifth semiconductor region and an element region, the element region including at least the third semiconductor region, the fourth semiconductor region and the gate electrode;
• and
• a sixth semiconductor region of the second conductivity type which is formed at or in the vicinity of the interface between the first semiconductor layer and the second semiconductor layer and is provided below at least the element region and the high-voltage withstand region, the sixth semiconductor region having an impurity concentration higher than that of the second semiconductor layer and formed into a given pattern having an extending part extending from the element region to the high-voltage withstand region and windows which are located at least below the element region to allow majority carriers in the first semiconductor layer to pass therethrough, whereby an electric resistance on carriers passing between the fifth semiconductor region and a portion of the second semiconductor layer at a distance from the fifth semiconductor region is reduced but carriers injection between the first semiconductor layer and the second semiconductor layer is allowed.