Method for manufacturing silicon carbide semiconductor device and silicon carbide semiconductor device
A method for manufacturing a silicon carbide semiconductor device includes the steps of preparing a silicon carbide substrate having a first main surface and a second main surface located on a side opposite to the first main surface, forming an epitaxial layer on the first main surface, the epitaxial layer having a first conductivity type and having a third main surface located on a side opposite to a side on which the silicon carbide substrate is located, forming a trench, which includes side walls intersecting with the third main surface and a bottom portion connected to the side walls, in the epitaxial layer, widening an opening of the trench, and forming an embedded region, which has a second conductivity type different from the first conductivity type, in the trench. The epitaxial layer adjacent to the embedded region and the embedded region constitute a superjunction structure.
1. A silicon carbide semiconductor device comprising:
a silicon carbide substrate having a first main surface and a second main surface located on a side opposite to said first main surface;
an epitaxial layer formed on said first main surface, said epitaxial layer having a first conductivity type and having a third main surface located on a side opposite to a side on which said silicon carbide substrate is located;
a trench which is formed in said epitaxial layer and includes side walls intersecting with said third main surface and a bottom portion connected to said side walls; and
an embedded region, which is formed in said trench and has a second conductivity type different from said first conductivity type, said trench being filled with said embedded region;
an opening of said trench being wider than said bottom portion, and said epitaxial layer adjacent to said embedded region and said embedded region constituting a superjunction structure, said silicon carbide semiconductor device further comprising:
an impurity region formed on said embedded region and having said second conductivity type;
a first electrode provided on said impurity region; and
a second electrode in contact with said second main surface.
2. The silicon carbide semiconductor device according to claim 1 , wherein said side walls are inclined by greater than or equal to 45° and less than or equal to 80° with respect to said third main surface.
3. The silicon carbide semiconductor device according to claim 1 , wherein
in said embedded region, a concentration of an impurity having said second conductivity type is reduced from said bottom portion toward said opening, and
in said epitaxial layer, a concentration of an impurity having said first conductivity type increases from said first main surface toward said third main surface.
4. The silicon carbide semiconductor device according to claim 1 , wherein said embedded region is in contact with said impurity region.
5. The silicon carbide semiconductor device according to claim 1 , wherein said bottom portion is in contact with said first main surface.
6. The silicon carbide semiconductor device according to claim 1 , wherein said trench extends along a <11-20>direction when viewed in a plan view.
7. The silicon carbide semiconductor device according to claim 6 , wherein a plurality of trenches and embedded regions are provided, and
the plurality of said trenches and said embedded regions are in stripe.