Semiconductor device having gate trenches and field plate trenches and a method of fabricating the semiconductor device
A semiconductor device includes: a plurality of transistor cells formed in a semiconductor body. The plurality of transistor cells includes: a plurality of stripe-shape gate trenches formed in a first main surface of the semiconductor body; and a plurality of field plate trenches separate from the stripe-shape gate trenches. At least one field plate trench is laterally interposed between each pair of neighboring stripe-shape gate trenches. Each stripe-shape gate trench includes a gate electrode, a gate dielectric between the gate electrode and a sidewall of the stripe-shape gate trench, and an oxide between the gate electrode and a bottom of the stripe-shape gate trench, the oxide having a vertical thickness that is greater than eight times a lateral thickness of the gate dielectric and/or greater than a vertical thickness of the gate electrode. A method of producing the semiconductor device is also described.
1 . A semiconductor device, comprising:
a semiconductor body; and
a plurality of transistor cells formed in the semiconductor body,
wherein the plurality of transistor cells comprises:
a plurality of stripe-shape gate trenches formed in a first main surface of the semiconductor body; and
a plurality of field plate trenches separate from the stripe-shape gate trenches, wherein at least one field plate trench is laterally interposed between each pair of neighboring stripe-shape gate trenches,
wherein each stripe-shape gate trench includes a gate electrode, a gate dielectric between the gate electrode and a sidewall of the stripe-shape gate trench, and an oxide between the gate electrode and a bottom of the stripe-shape gate trench, the oxide having a vertical thickness that is greater than eight times a lateral thickness of the gate dielectric and/or greater than a vertical thickness of the gate electrode,
wherein the field plate trenches are needle-shape and arranged in a grid between pairs of neighboring stripe-shape gate trenches,
wherein the stripe-shape gate trenches are wider and deeper than the field plate trenches.
2 . The semiconductor device of claim 1 , wherein the stripe-shape gate trenches extend into a drift zone common to the plurality of transistor cells, and wherein the oxide in the stripe-shape gate trenches terminates at a depth in the semiconductor body that corresponds to at least 30% of a vertical thickness of the drift zone.
3 . The semiconductor device of claim 2 , wherein the oxide in the stripe-shape gate trenches terminates at a depth in the semiconductor body that corresponds to at least 50% of the vertical thickness of the drift zone.
4 . The semiconductor device of claim 1 , wherein the oxide in the stripe-shape gate trenches is under compressive stress and a region of the semiconductor body that adjoins the oxide has tensile strain such that carrier mobility is increased in the region of the semiconductor body that adjoins the oxide.
5 . The semiconductor device of claim 4 , wherein the stripe-shape gate trenches extend into a drift zone common to the plurality of transistor cells, and wherein a region of the drift zone that adjoins the oxide has tensile strain over at least 30% of a vertical thickness of the drift zone.
6 . The semiconductor device of claim 1 , wherein a field plate in each field plate trench comprises an integrated diode.
7 . The semiconductor device of claim 6 , wherein the integrated diode comprises an anode and a cathode below the anode and having a greater vertical thickness than the anode.
8 . The semiconductor device of claim 7 , wherein with reference to the first main surface of the semiconductor body, a pn junction between a body region and a drift zone of the plurality of transistor cells is shallower than a pn junction between the anode and the cathode of each integrated diode.
9 . The semiconductor device of claim 7 , wherein with reference to the first main surface of the semiconductor body, a pn junction between a body region and a drift zone of the plurality of transistor cells is deeper than a pn junction between the anode and the cathode of each integrated diode.
10 . The semiconductor device of claim 7 , wherein the field plate trenches are recessed below the first main surface of the semiconductor body such that the anode of each integrated diode is disposed below a level of a source region of the plurality of transistor cells.
11 . The semiconductor device of claim 1 , wherein each field plate trench includes a field plate, a dielectric between the field plate and a sidewall of the field plate trench, and an oxide between the field plate and a bottom of the field plate trench, the oxide having a vertical thickness that is greater than a lateral thickness of the dielectric.
12 . A semiconductor device, comprising:
a semiconductor body; and
a plurality of transistor cells formed in the semiconductor body,
wherein the plurality of transistor cells comprises:
a plurality of stripe-shape gate trenches formed in a first main surface of the semiconductor body; and
a plurality of field plate trenches separate from the stripe-shape gate trenches, wherein at least one field plate trench is laterally interposed between each pair of neighboring stripe-shape gate trenches,
wherein each stripe-shape gate trench includes a gate electrode, a gate dielectric between the gate electrode and a sidewall of the stripe-shape gate trench, and an oxide between the gate electrode and a bottom of the stripe-shape gate trench, the oxide having a vertical thickness that is greater than eight times a lateral thickness of the gate dielectric and/or greater than a vertical thickness of the gate electrode,
wherein a field plate in each field plate trench comprises an integrated diode.
13 . The semiconductor device of claim 12 , wherein the integrated diode comprises an anode and a cathode below the anode and having a greater vertical thickness than the anode.
14 . The semiconductor device of claim 13 , wherein with reference to the first main surface of the semiconductor body, a pn junction between a body region and a drift zone of the plurality of transistor cells is shallower than a pn junction between the anode and the cathode of each integrated diode.
15 . The semiconductor device of claim 13 , wherein with reference to the first main surface of the semiconductor body, a pn junction between a body region and a drift zone of the plurality of transistor cells is deeper than a pn junction between the anode and the cathode of each integrated diode.
16 . The semiconductor device of claim 13 , wherein the field plate trenches are recessed below the first main surface of the semiconductor body such that the anode of each integrated diode is disposed below a level of a source region of the plurality of transistor cells.
17 . A semiconductor device, comprising:
a semiconductor body; and
a plurality of transistor cells formed in the semiconductor body,
wherein the plurality of transistor cells comprises:
a plurality of stripe-shape gate trenches formed in a first main surface of the semiconductor body; and
a plurality of field plate trenches separate from the stripe-shape gate trenches, wherein at least one field plate trench is laterally interposed between each pair of neighboring stripe-shape gate trenches,
wherein each stripe-shape gate trench includes a gate electrode, a gate dielectric between the gate electrode and a sidewall of the stripe-shape gate trench, and an oxide between the gate electrode and a bottom of the stripe-shape gate trench, the oxide having a vertical thickness that is greater than eight times a lateral thickness of the gate dielectric and/or greater than a vertical thickness of the gate electrode,
wherein each field plate trench includes a field plate, a dielectric between the field plate and a sidewall of the field plate trench, and an oxide between the field plate and a bottom of the field plate trench, the oxide having a vertical thickness that is greater than a lateral thickness of the dielectric.