Trench transistors and methods with low-voltage-drop shunt to body diode
Methods and systems for power semiconductor devices integrating multiple trench transistors on a single chip. Multiple power transistors (or active regions) are paralleled, but one transistor has a lower threshold voltage. This reduces the voltage drop when the transistor is forward-biased. In an alternative embodiment, the power device with lower threshold voltage is simply connected as a depletion diode, to thereby shunt the body diodes of the active transistors, without affecting turn-on and ON-state behavior.
1. A power semiconductor device, comprising:
a first-conductivity-type source region;
a first trench containing a gate electrode which is capacitively coupled to a body region to selectably form a channel region therein;
at least one second trench containing a recessed field plate electrode;
a body contact region which is more heavily doped than said body region;
a plurality of shield regions; wherein one said shield region is present beneath at least each said second trench;
a source metallization layer which is in ohmic contact with said source region and said body contact region, and which is electrically connected to said gate electrode; and
a backside metallization layer.
2. The device of claim 1 , wherein one said shield region is present beneath said first trench.
3. The device of claim 1 , wherein said body contact region extends to one said shield region.
4. The device of claim 1 , wherein said gate electrode is a split gate electrode.
5. The device of claim 1 , wherein said shield regions are second-conductivity-type regions.
6. The device of claim 1 , wherein said first trench has a thick bottom oxide.
7. The device of claim 1 , wherein said first conductivity type is N type.
8. The device of claim 1 , further comprising first and second wherein each said first trench-gated transistors, and wherein each said first trench-gated transistor has a lower threshold voltage than each said second trench-gated transistor.
9. The device of claim 8 , further comprising at least one field plate electrode separating said trench-gated transistors.
10. The device of claim 1 , further comprising a second-conductivity-type shield region beneath at least one said gate electrode.
11. The device of claim 1 , wherein at least one said gate electrode is a split gate electrode.
12. The device of claim 1 , constructed in a semiconductor die which is made of silicon.