Semiconductor device and manufacturing method thereof

A semiconductor device including a pnpn structure in which main current flows between first and second main surfaces sandwiching an intrinsic or a first conductivity type semiconductor substrate, comprising:

• a first impurity region of a first conductivity type formed at said first main surface of said semiconductor substrate;
• a second impurity region of a second conductivity type formed at said second main surface of said semiconductor substrate;
• and
• a third impurity region of the second conductivity type formed below said first impurity region and sandwiching, with said second impurity region, a region of said semiconductor substrate;
• wherein
• said semiconductor substrate has a plurality of trenches extending parallel to each other at said first main surface, each said trench being formed to reach said region of said semiconductor substrate from said first main surface through said first and third impurity regions,
• said first impurity region being formed entirely over said first main surface of said semiconductor substrate between said trenches extending parallel to each other;
• said device further comprising:
• a control electrode layer formed in said trench to oppose to said region of said semiconductor substrate and said first and third impurity regions with an insulating film interposed;
• a first electrode layer formed on said first main surface of said semiconductor substrate and electrically connected to said first impurity region;
• a second electrode layer formed on said second main surface of said semiconductor substrate and electrically connected to said second impurity region;
• said plurality of trenches includes first, second and third trenches extending parallel to each other;
• said first impurity region being formed entirely at said first main surface of said semiconductor substrate between said first and second trenches;
• a fourth impurity region of the second conductivity type is formed at said first main surface of said semiconductor substrate between said second and third trenches, and
• said fourth impurity region being made shallower than said trench and electrically connected to said first electrode layer.