Bidirectional JFET and a process of forming the same
An electronic device comprising a bidirectional JFET can include a drain/source region; a lightly doped semiconductor layer overlying the drain/source region; a source/drain region overlying the lightly doped semiconductor layer; a trench extending through the source/drain region and into the lightly doped semiconductor layer; a gate electrode of the bidirectional JFET within the trench; and a field electrode within the trench. A process of forming an electronic device can include providing a workpiece including a first doped region and a lightly doped semiconductor layer overlying the first doped region; defining a trench extending into the lightly doped semiconductor layer; forming a gate electrode within the trench, wherein the gate electrode extends to a sidewall of the trench; and forming a field electrode within the trench, wherein a bidirectional JFET includes the first doped region, the lightly doped semiconductor layer, a second doped region, and the gate electrode.
1. An electronic device comprising a bidirectional junction field-effect transistor comprising:
a drain/source region having a first conductivity type;
a lightly doped semiconductor layer overlying the drain/source region;
a source/drain region having the first conductivity type and overlying the drain/source region and the lightly doped semiconductor layer;
a first trench extending into the lightly doped semiconductor layer;
an insulating layer lying along a bottom and sidewall of the first trench;
a gate electrode within the first trench and spaced apart from the drain/source region and the source/drain region, wherein the gate electrode is electrically isolated from the bottom of the first trench by at least the insulating layer;
a first doped region having a second conductivity type opposite the first conductivity type; and
a first field electrode within the first trench,
wherein:
the first doped region is spaced apart from the drain/source region and the source/drain region,
no other region of the second conductivity type is disposed between the first doped region and each of the drain/source and source/drain regions,
no other region of the second conductivity type is disposed between the bottom of the first trench and the drain/source region, and
the first doped region is adjacent to the first trench and electrically connected to the gate electrode.
2. The electronic device of claim 1 , wherein the first field electrode is electrically connected to the gate electrode.
3. The electronic device of claim 1 , wherein the first doped region has a conductivity type opposite a conductivity type of the lightly doped semiconductor layer.
4. The electronic device of claim 1 , further comprising:
a second trench extending into the lightly doped semiconductor layer, wherein the first and second trenches are spaced apart from each other; and
a second doped region disposed between the drain/source region and the source/drain region, adjacent to the second trench, spaced apart from the first doped region by a portion of the lightly doped semiconductor layer, and electrically connected to the gate electrode.
5. The electronic device of claim 1 , wherein the first field electrode is an only field electrode within the first trench and is electrically connected to the gate electrode.
6. The electronic device of claim 1 , further comprising a second field electrode within the first trench, wherein no combination of the gate electrode, the first field electrode, and the second field electrode are electrically connected to one another.
7. The electronic device of claim 6 , wherein:
the first field electrode is electrically connected to the source/drain region and lies closer to the drain/source region than to the source/drain region; and
the second field electrode is electrically connected to the drain/source region and lies closer to the source/drain region lies than to the drain/source region.
8. The electronic device of claim 7 , wherein each of the first and second field electrodes is not electrically connected to the drain/source region, the source/drain region, or the gate electrode.
9. The electronic device of claim 1 , wherein the bidirectional junction field-effect transistor has a voltage rating of at least 150 V in both current directions of the bidirectional junction field-effect transistor.
10. The electronic device of claim 1 , wherein:
the drain/source region, the source/drain region, and the lightly doped semiconductor layer include n-type GaN; and
the doped region includes p-type GaN.
11. A process of forming an electronic device comprising:
providing a workpiece including a drain/source region and a lightly doped semiconductor layer overlying the drain/source region, wherein the drain/source region has a first conductivity type;
patterning the lightly doped semiconductor layer to define a trench extending into the lightly doped semiconductor layer;
forming a first doped region within the lightly doped semiconductor layer, wherein the first doped region has a second conductivity type opposite the first conductivity type; and
forming a first insulating layer along a bottom and sidewall of the trench;
forming a gate electrode within the trench after forming the first insulating layer,
wherein:
the gate electrode extends to a sidewall of the trench and is spaced apart from the drain/source region, and
the gate electrode is electrically isolated from the bottom of the trench by at least the first insulating layer;
forming a second insulating layer within the trench after forming the gate electrode;
forming a first field electrode within the trench; and
forming a source/drain region having the first conductivity type such that the source/drain region overlies the drain/source region and the lightly doped semiconductor layer,
wherein in a finished device:
a bidirectional junction field-effect transistor includes the drain/source region, the first doped region, the lightly doped semiconductor layer, the gate electrode, and the source/drain region,
the first doped region is spaced apart from the drain/source region and the source/drain region,
no other region of the second conductivity type is disposed between the first doped region and each of the drain/source and source/drain regions,
no other region of the second conductivity type is disposed between the bottom of the trench and the drain/source region, and
the first doped region is adjacent to the sidewall of the trench and electrically connected to the gate electrode.
12. The process of claim 11 , further comprising forming a second doped region along a portion of a sidewall of the trench after forming the trench.
13. The process of claim 12 , wherein the second doped region extends laterally across part of and not all of the lightly doped semiconductor layer.
14. The process of claim 13 , wherein forming the first doped region comprises diffusing dopant from the gate electrode into the lightly doped semiconductor layer.
15. The process of claim 12 , wherein forming the second doped region is performed before patterning the lightly doped semiconductor layer.
16. The process of claim 12 , wherein forming the second doped region is performed by diffusing a dopant from the gate electrode into the lightly doped semiconductor layer.
17. The process of claim 12 , wherein patterning the lightly doped semiconductor layer to define the trench is performed after forming the first doped region, and the trench extends through the first doped region.
18. The process of claim 11 , further comprising forming a backside contact to the first doped region.
19. The process of claim 11 , further comprising:
forming a second field electrode within the trench; and
forming a third insulating layer within the trench after forming the second field electrode,
wherein forming the first field electrode is performed before forming the gate electrode, and forming the second field electrode is formed after forming the second insulating layer.
20. The process of claim 11 , wherein the first field electrode is an only field electrode within the trench.