Transistor device
A transistor device includes a semiconductor substrate having a first major surface, a cell field, and an edge termination region laterally surrounding the cell field. The cell field includes elongate trenches that extend from the first major surface into the semiconductor substrate and that are positioned substantially parallel to one another such that one or more inner elongate trenches are arranged between two outermost elongate trenches and elongate mesas, each elongate mesa being formed between neighbouring elongate trenches. The elongate mesas include a drift region, a body region on the drift region and a source region on the body region. In a top view, one or both of the outermost elongate trenches has a different contour from the one or more inner elongate trenches.
1. A transistor device, comprising:
a semiconductor substrate having a first major surface, a cell field, and an edge termination region laterally surrounding the cell field, wherein the cell field comprises:
a plurality of elongate trenches that extend from the first major surface into the semiconductor substrate and that are positioned substantially parallel to one another such that one or more inner elongate trenches are arranged between two outermost elongate trenches; and
elongate mesas, each elongate mesa being formed between neighbouring elongate trenches, wherein the elongate mesas comprise a drift region, a body region on the drift region and a source region on the body region,
wherein in a top view, one or both of the outermost elongate trenches has a different contour from the one or more inner elongate trenches,
wherein the edge termination region comprises an edge trench that extends from the first major surface into the semiconductor substrate and that laterally surrounds the cell field,
wherein the edge trench comprises longitudinal trench portions and transverse trench portions that extend between the longitudinal trench portions such that an inner trench corner is formed at each intersection between an inner side wall of the longitudinal trench portion and an inner side wall of the transverse trench portion,
wherein an edge mesa is formed between the edge trench and the cell field, and
wherein the inner trench corner of the edge trench has a radius of curvature that is greater than the width of the edge mesa measured between the longitudinal trench portion and a longitudinal side wall of the outermost elongate trench and/or the inner trench corner of the edge trench has a radius of curvature that is greater than the width of the elongate mesa.
2. The transistor device of claim 1 , wherein the radius of curvature of the inner trench corner of the edge trench is at least 1 μm.
3. The transistor device of claim 1 , wherein the width of the edge mesa lies in a range of 0.1 μm and 2 μm and/or the elongate trenches and the elongate mesas have a width that lies in a range of 0.1 μm and 2 μm.
4. The transistor device of claim 1 , wherein the outermost elongate trench has an outer corner facing towards the edge termination region and an inner corner facing towards an inner elongate trench, and wherein the outer corner and the inner corner have a differing radius of curvature.
5. The transistor device of claim 4 , wherein the outer corner has a radius of curvature R 1 that is greater than a radius of curvature R 2 of the inner corner.
6. The transistor device of claim 5 , wherein in plan view, the corners of the inner elongate trenches have substantially a same radius of curvature R 3 .
7. The transistor device of claim 6 , wherein R 1 >R 3 .
8. The transistor device of claim 6 , wherein R 1 >R 2 >R 3 .
9. The transistor device of claim 1 , further comprising a further active cell field arranged laterally adjacent the cell field in the semiconductor substrate, wherein the further active cell field is surrounded by a further edge trench and a further edge mesa.
10. The transistor device of claim 1 , further comprising a field plate positioned in each elongate trench.
11. The transistor device of claim 10 , further comprising elongate gate trenches that extend parallel to the elongate trenches and comprising a gate electrode, or a planar gate electrode positioned on one or more of the elongate mesas.
12. The transistor device of claim 1 , further comprising a gate electrode positioned in each elongate trench, or a gate electrode positioned in two or more of the elongate gate trenches.
13. The transistor device of claim 1 , further comprising a gate electrode arranged above and electrically insulated from a field plate.
14. A transistor device, comprising:
a semiconductor substrate having a first major surface, a cell field, and an edge termination region laterally surrounding the cell field, wherein the cell field comprises:
a plurality of elongate trenches that extend from the first major surface into the semiconductor substrate and that are positioned substantially parallel to one another such that one or more inner elongate trenches are arranged between two outermost elongate trenches;
elongate mesas, each elongate mesa being formed between neighbouring elongate trenches, wherein the elongate mesas comprise a drift region, a body region on the drift region and a source region on the body region;
wherein the edge termination region comprises an edge trench that extends from the first major surface into the semiconductor substrate and that laterally surrounds the cell field,
wherein the edge trench comprises longitudinal trench portions and transverse trench portions that extend between the longitudinal trench portions such that an inner trench corner is formed at each intersection between an inner side wall of the longitudinal trench portion and an inner side wall of the transverse trench portion,
wherein the inner trench corner of the edge trench has a radius of curvature and wherein an edge mesa is formed between the edge trench and the cell field,
wherein one or both of the outermost elongate trenches has an outer corner facing towards the edge termination region and an inner corner facing towards an inner elongate trench,
wherein a difference between a width of the edge mesa measured between the inner corner of the edge trench and the outer corner of the outermost elongate trench and a width of the edge mesa measured between the longitudinal trench portion and a longitudinal side wall of the outermost elongate trench is less than 10%,
wherein the outermost elongate trench has an outer corner facing towards the edge termination region and an inner corner facing towards an inner elongate trench,
wherein the outer corner and the inner corner have a differing radius of curvature.
15. The transistor device of claim 14 , wherein the outer corner has a radius of curvature R 1 that is greater than a radius of curvature R 2 of the inner corner.
16. The transistor device of claim 15 , wherein in plan view, the corners of the inner elongate trenches have substantially a same radius of curvature R 3 .
17. The transistor device of claim 16 , wherein R 1 >R 3 .
18. The transistor device of claim 16 , wherein R 1 >R 2 >R 3 .
19. The transistor device of claim 14 , further comprising a further active cell field arranged laterally adjacent the cell field in the semiconductor substrate, wherein the further active cell field is surrounded by a further edge trench and a further edge mesa.
20. The transistor device of claim 14 , further comprising a field plate positioned in each elongate trench.
21. The transistor device of claim 20 , further comprising elongate gate trenches that extend parallel to the elongate trenches and comprising a gate electrode, or a planar gate electrode positioned on one or more of the elongate mesas.
22. The transistor device of claim 14 , further comprising a gate electrode positioned in each elongate trench, or a gate electrode positioned in two or more of the elongate gate trenches.
23. The transistor device of claim 14 , further comprising a gate electrode arranged above and electrically insulated from a field plate.
24. The transistor device of claim 14 , wherein in a top view, one or both of the outermost elongate trenches has a different contour from the inner elongate trenches.
25. A transistor device, comprising:
a semiconductor substrate having a first major surface, a cell field, and an edge termination region laterally surrounding the cell field, wherein the cell field comprises:
a plurality of elongate trenches that extend from the first major surface into the semiconductor substrate and that are positioned substantially parallel to one another such that one or more inner elongate trenches are arranged between two outermost elongate trenches; and
elongate mesas, each elongate mesa being formed between neighbouring elongate trenches, wherein the elongate mesas comprise a drift region, a body region on the drift region and a source region on the body region,
wherein in a top view, one or both of the outermost elongate trenches has a different contour from the one or more inner elongate trenches,
wherein the outermost elongate trench has an outer corner facing towards the edge termination region and an inner corner facing towards an inner elongate trench,
wherein the outer corner and the inner corner have a differing radius of curvature.
26. The transistor device of claim 25 , wherein the outer corner has a radius of curvature R 1 that is greater than a radius of curvature R 2 of the inner corner.
27. The transistor device of claim 26 , wherein in plan view, the corners of the inner elongate trenches have substantially a same radius of curvature R 3 .
28. The transistor device of claim 27 , wherein R 1 >R 3 .
29. The transistor device of claim 27 , wherein R 1 >R 2 >R 3 .