Semiconductor schottky device with pn regions

A semiconductor device having:

• a semiconductor substrate having a pair of one and the other main surfaces opposite to each other and having, between said pair of main surfaces, a first semiconductor region of one conductive type being adjacent to said one main surface, a second semiconductor region of one conductive type being adjacent to both said first semiconductor region and said other main surface and having an impurity concentration lower than that of said first semiconductor region, a third semiconductor region of the other conductive type extending from said other main surface into the inside of said second semiconductor region so as to form small areas and an annular area surrounding said small areas when seen from said other main surface and having an impurity concentration higher than that of said second semiconductor region, and a fourth semiconductor region of the other conductive type extending from said other main surface into the inside of said second semiconductor region so as to be located on portions of said second semiconductor region which are exposed among said small and annular areas of said third semiconductor region, said fourth semiconductor region and having a thickness thinner than that of said third semiconductor region and having an impurity concentration lower than that of said third semiconductor region;
• a first electrode provided at said one main surface of said semiconductor substrate so as to be in ohmic contact with said first semiconductor region;
• and
• a second electrode provided at said other main surface of said semiconductor substrate so as to be in ohmic contact with said third semiconductor region and so as to be in contact through a Schottky barrier with said third semiconductor region.

A semiconductor device comprising:

• a first semiconductor region of one conductive type;
• a second semiconductor region of the other conductive type extending from one surface of said first semiconductor region into the inside of said first semiconductor region so as to form small areas and an annular area surrounding said small areas when seen from said one surface and having an impurity concentration higher than that of said first semiconductor region;
• a third semiconductor region of the other conductive type extending from said one surface of said first semiconductor region into the inside of said first semiconductor region so as to be located on portions of said first semiconductor region which are exposed among said small and annular areas of said second semiconductor region, said third semiconductor region having a thickness thinner than that of said second semiconductor region and having an impurity concentration lower than that of said second semiconductor region;
• a fourth semiconductor region of the one conductive type provided so as to be adjacent to said first semiconductor region at an opposite side to said one surface, said fourth semiconductor region partly extending to said one surface so as to be exposed at said one surface and having an impurity concentration higher than that of said first semiconductor region;
• a first electrode provided so as to be in ohmic contact with said second semiconductor region and so as to be in contact through a Schottky barrier with said third semiconductor region;
• and
• a second electrode provided so as to be in ohmic contact with the portion of said fourth semiconductor region which is exposed at said one surface.