Semiconductor device and manufacturing method thereof

A method of manufacturing a semiconductor device in which current flows between first and second main surfaces of an intrinsic or a first conductivity type semiconductor substrate, comprising the steps of

• forming a first impurity region of a second conductivity type by performing selective ion implantation on said first main surface of the semiconductor device of the first conductivity type;
• forming a second impurity region of the second conductivity type at said second main surface of said semiconductor substrate;
• forming a third impurity region of the first conductivity type at said first main surface in said first impurity region by selective ion implantation;
• forming a plurality of trenches including a first, second and third trenches in said semiconductor substrate by performing anisotropic etching on said first main surface;
• wherein
• the first and third impurity regions are positioned at said first main surface between said first and second trenches, and only a low impurity concentration region of said semiconductor substrate is positioned at said first main surface between said second and third trenches;
• said method further comprising the steps of:
• forming a control electrode layer in said trench to oppose to the low concentration region of said semiconductor substrate sandwiched between said first and second impurity regions and to said first and third impurity regions, with an insulating film interposed;
• forming a fourth impurity region of the second conductivity type having higher impurity concentration than said first impurity region at said first main surface in said first impurity region to be adjacent to said third impurity region by selective ion implantation;
• forming a first electrode layer on said first main surface to be electrically connected to said third and fourth impurity regions;
• and
• forming a second electrode layer on said second main surface to be electrically connected to said second impurity region.