SEMICONDUCTOR DEVICES WITH DRAIN-SOURCE CONNECTION FOR AVALANCHE BREAKDOWN
A vertical junction field effect (JFET) semiconductor device according to some embodiments includes a drift layer, a channel layer on the drift layer, and a plurality of alternating trenches and mesas in the channel layer, wherein a first plurality of the trenches includes gate contact regions. A source metallization is on the mesas. The device includes a second different than the first plurality of trenches, wherein the source metallization is electrically connected to the drift layer at a bottom of the second trench.
1 . A vertical junction field effect (JFET) semiconductor device, comprising:
a drift layer;
a channel layer on the drift layer;
a plurality of alternating trenches and mesas in the channel layer, wherein a first plurality of the trenches comprises gate contact regions;
a source metallization on the mesas; and
a second trench different than the first plurality of trenches, wherein the source metallization is electrically connected to the drift layer at a bottom of the second trench.
2 . The vertical JFET semiconductor device of claim 1 , wherein the source metallization extends into the second trench.
3 . The vertical JFET semiconductor device of claim 1 , further comprising:
an electrical contact in the second trench, wherein the electrical contact is electrically connected to the source metallization outside the second trench.
4 . The vertical JFET semiconductor device of claim 1 , wherein the second trench extends deeper into the drift layer than the first plurality of trenches.
5 . The vertical JFET semiconductor device of claim 1 , wherein the second trench extends about two to three times deeper into the drift layer than the first plurality of trenches.
6 . The vertical JFET semiconductor device of claim 1 , wherein corners of a pair of mesas of the plurality of mesas adjacent the second trench are rounded, angled or chamfered.
7 . The vertical JFET semiconductor device of claim 1 , wherein a first one of the first plurality of trenches is directly adjacent a second one of the first plurality of trenches, wherein a distance between the first and second ones of the first plurality of trenches is greater than a distance between the second trench and a third one of the first plurality of trenches that is directly adjacent to the second trench.
8 . The vertical JFET semiconductor device of claim 1 , further comprising a doped region beneath the second trench, wherein the doped region has a conductivity type that is the same as a conductivity type of a drift region of the vertical JFET semiconductor device.
9 . The vertical JFET semiconductor device of claim 8 , wherein the second trench is deeper than the first plurality of trenches.
10 . The vertical JFET semiconductor device of claim 8 , wherein the doped region has a greater doping concentration than the drift region.
11 . The vertical JFET semiconductor device of claim 8 , wherein the doped region has a doping concentration greater than about 1.25 times a doping concentration of the drift region.
12 . The vertical JFET semiconductor device of claim 1 , wherein the second trench is enclosed by a single mesa.
13 . The vertical JFET semiconductor device of claim 1 , further comprising a plurality of second trenches, wherein the source metallization is electrically connected to the drift layer at bottoms of the plurality of second trenches.
14 . The vertical JFET semiconductor device of claim 13 , wherein bottoms of the plurality of second trenches are conductively connected to the source metallization.
15 . The vertical JFET semiconductor device of claim 14 , wherein a number of the first plurality of trenches is about equal to a number of the plurality of second trenches.
16 . The vertical JFET semiconductor device of claim 14 , wherein each of the plurality of second trenches is adjacent one of the first plurality of trenches.
17 . A vertical junction field effect (JFET) semiconductor device, comprising:
a drift layer;
a channel layer on the drift layer;
a plurality of alternating trenches and mesas in the channel layer, wherein a first plurality of the trenches comprise gate contact regions; and
a source metallization on the plurality of alternating trenches and mesas;
wherein the source metallization is electrically connected to the drift layer at a bottom of a second trench that is different from the first plurality of trenches.
18 . The vertical JFET semiconductor device of claim 17 , further comprising a plurality of second trenches, wherein the source metallization is electrically connected to the drift layer at bottoms of the plurality of second trenches.
19 . A vertical junction field effect (JFET) semiconductor device, comprising:
a drift layer;
a channel layer on the drift layer; and
a plurality of alternating trenches and mesas in the channel layer within an active region of the device, wherein the plurality of trenches comprise a first plurality of the trenches having a first depth and a second plurality of trenches in having a second depth that is greater than the first depth.
20 . The vertical JFET semiconductor device of claim 19 , further comprising:
gate contact regions within the first plurality of trenches; and
a source metallization, wherein the source metallization is electrically connected to the drift layer at bottoms of the second plurality of trenches.
21 . A method of forming vertical junction field effect (JFET) semiconductor device, comprising:
providing a drift layer;
forming a channel layer on the drift layer; and
forming a plurality of alternating trenches and mesas in the channel layer within an active region of the device, wherein the plurality of trenches comprise a first plurality of the trenches having a first depth and a second plurality of trenches having a second depth that is greater than the first depth.
22 . The method of claim 21 , further comprising:
forming gate contacts within the first plurality of trenches; and
forming a source metallization on the device, wherein the source metallization is electrically connected to the drift layer at bottoms of the second plurality of trenches.