Trench transistors and methods with low-voltage-drop shunt to body diode
View Patent ↗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:
first and second trench-gated transistors integrated on a semiconductor die, both having a portion of a first-conductivity-type source region, and a gate electrode which is capacitively coupled to a body region to selectably form a channel region therein;
wherein said first trench-gated transistor has a lower threshold voltage than does said second trench-gated transistor; and
wherein said second trench-gated transistor, but not said first trench-gated transistor, is a primary switching transistor.
2. The device of claim 1 , wherein, in said first trench-gated transistor but not said second trench-gated transistor, the gate electrode is shorted to the source region.
3. The device of claim 1 , wherein both said trench-gated transistors are identically electrically connected.
4. The device of claim 1 , further comprising at least one field plate electrode separating said first and second trench-gated transistors.
5. The device of claim 1 , further comprising a second-conductivity-type shield region beneath at least one said gate electrode.
6. The device of claim 1 , wherein at least one said gate electrode is a split gate electrode.
7. The device of claim 1 , wherein at least one said gate electrode is contained in a trench having a thick bottom oxide.
8. The device of claim 1 , wherein said first conductivity type is N type.
9. The device of claim 1 , wherein said semiconductor die is made of silicon.
10. A power semiconductor device, comprising:
first and second trench-gated transistors both having a portion of a first-conductivity-type source region, and a gate electrode which is capacitively coupled to a body region to selectably form a channel region therein;
wherein said first and second trench-gated transistors are integrated on a single semiconductor die;
wherein said second trench-gated transistor has a longer channel length than does said first trench-gated transistor; and
wherein said second trench-gated transistor, but not said first trench-gated transistor, is a primary switching transistor.
11. The device of claim 10 , wherein the body region of said second trench-gated transistor is deeper than the body region of said first trench-gated transistor.
12. The device of claim 10 , wherein, in said first trench-gated transistor but not said second trench-gated transistor, the gate electrode is shorted to a common source electrode.
13. The device of claim 10 , wherein both said trench-gated transistors are identically electrically connected.
14. The device of claim 10 , further comprising at least one field plate electrode separating said first and second trench-gated transistors.
15. The device of claim 14 , further comprising a second-conductivity-type shield region beneath at least one said field plate electrode.
16. The device of claim 10 , further comprising a second-conductivity-type shield region beneath at least one said gate electrode.
17. The device of claim 10 , wherein at least one said gate electrode is a split gate electrode.
18. The device of claim 10 , wherein at least one said gate electrode is contained in a trench having a thick bottom oxide.
19. The device of claim 10 , wherein said first conductivity type is N type.
20. A power semiconductor device, comprising:
one or more first trench-gated transistors, each having a portion of a first-conductivity-type source region, and a first gate electrode which is capacitively coupled to a first body region to selectably form a first channel region therein;
one or more second trench-gated transistors, each having a portion of said first-conductivity-type source region, and a second gate electrode which is capacitively coupled to a second body region to selectably form a second channel region therein;
wherein said trench-gated transistors are integrated on a single semiconductor die;
wherein said second body regions are deeper than said first body regions, and said second channel regions are longer than said first channel regions;
wherein each said first trench-gated transistor has a lower threshold voltage than does each said second trench-gated transistor; and
wherein said one or more second trench-gated transistors, but not said one or more first trench-gated transistors, are primary switching transistors.