Semiconductor device comprising bipolar and unipolar transistors including a concave and convex portion

A semiconductor device having at least one or more bipolar transistors and at least one or more unipolar transistors disposed on a semiconductor substrate of a first conductivity type and made of a semiconductor material with a band gap larger than silicon, the semiconductor device comprising:

• a first semiconductor layer of the first conductivity type and constituting the semiconductor substrate on a first principal surface side of the semiconductor substrate;
• a second semiconductor layer of the first conductivity type and constituting the semiconductor substrate on a second principal surface side of the semiconductor substrate, the second semiconductor layer having an impurity concentration higher than the first semiconductor layer;
• a third semiconductor layer of the first conductivity type disposed between the first semiconductor layer and the second semiconductor layer to be in contact with at least the first semiconductor layer;
• a concave portion disposed on the second principal surface side of the semiconductor substrate and penetrating the second semiconductor layer to the third semiconductor layer;
• a fourth semiconductor layer of a second conductivity type and disposed on a bottom surface of the concave portion to be in contact with the third semiconductor layer;
• an output electrode of the bipolar transistor, contacting the fourth semiconductor layer;
• an input electrode and a control electrode of the bipolar transistor disposed on the first principal surface side of the semiconductor substrate at a position corresponding to the concave portion;
• a convex portion formed on the second principal surface side of the semiconductor substrate, correspondingly to the concave portion;
• an output electrode of the unipolar transistor disposed on a surface of the convex portion to be electrically connected to the output electrode of the bipolar transistor;
• an input electrode of the unipolar transistor disposed on the first principal surface side of the semiconductor device at a position corresponding to the convex portion to be electrically connected to the input electrode of the bipolar transistor;
• and
• a control electrode of the unipolar transistor disposed on the first principal surface side of the semiconductor device at a position corresponding to the convex portion to be electrically connected to the control electrode of the bipolar transistor.