Trenched MOS gate controlled rectifier
A trenched MOS gate controlled rectifier has an asymmetric trench structure between the active area of active trenches and the termination area of termination trenches. The asymmetric trench structure has a gate electrode on one side of the trench to turn on and off the channel of the MOS structure effectively and a field plate structure on the other side with field dielectric sufficiently thick in order to sustain the high electric field during the reverse bias condition.
1. A semiconductor chip, comprising:
an asymmetric trench structure disposed at the border of an active area and a termination area of the semiconductor chip, the asymmetric trench structure comprising;
a first trench with opening at a top surface of the chip and having a first and a second sidewalls of an epitaxial semiconductor material, the first sidewall adjacent to the active area and the second sidewall adjacent to the termination area;
a field plate in the first trench, extending from the top surface into first trench; and
a second trench in the first trench, the second trench with opening at near the top surface, having sidewalls of dielectric material,
a gate electrode disposed in the second trench on one side of the field plate near the first sidewall and no gate electrode disposed on the opposite side of the field plate near the second sidewall; and
a first symmetrical trench, structure adjacent to the asymmetrical trench structure, disposed in the active area; and a second symmetrical structure adjacent to the asymmetrical trench structure, disposed in the termination area; wherein a conductive layer extends over and is in contact with a gate electrode and a field plate of the first symmetrical trench and contacts the gate electrode and the field plate of the asymmetrical trench structure.
2. The semiconductor chip of claim 1 , in which the gate electrode is separated from the sidewall of the epitaxial semiconductor material by a first dielectric layer of a first thickness and separated from the field plate by a second dielectric layer of a different thickness from the first thickness.
3. The semiconductor chip of the claim 2 , in which the gate electrode and the field plate are connected by a conductive layer at near the top surface of the chip.
4. The semiconductor chip of claim 1 , in which the first symmetric trench and the second symmetric trench structure are disposed adjacent to the asymmetric trench structure.
5. The semiconductor chip of claim 4 , in which the first symmetric trench has two gate electrodes adjacent to sidewalls of the first symmetric trench.
6. The semiconductor chip of claim 5 , in which the second symmetric trench has no gate electrode.
7. The semiconductor chip of claim 6 , in which the one gate electrode in the asymmetric trench is separated from a sidewall of the epitaxial semiconductor material by a gate dielectric.
8. The semiconductor chip of claim 7 , further comprising a first mesa separating the asymmetric trench from the first symmetric trench and a second mesa separating the asymmetric trench from the second symmetric trench.
9. The semiconductor chip of claim 8 , in which a conductive layer connects the first mesa at the top surface of the chip and the field plate but does not connect the second mesa at the top surface of the chip.