Trench gate laterally diffused MOSFET devices and methods for making such devices
First Claim
1. A method for making a MOSFET, comprising:
- providing a substrate including an epitaxial layer;
forming a first trench in the epitaxial layer;
filling the first trench with an insulating layer;
forming a second trench in the insulating layer such that the second trench is not symmetric relative to the first trench;
filling the second trench with a conductive material; and
forming a plurality of dopant regions adjacent the first trench with a first one of the plurality of dopant regions extending under the first trench.
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0 Petitions
Accused Products
Abstract
A MOSFET device for RF applications that uses a trench gate in place of the lateral gate used in lateral MOSFET devices is described. The trench gate in the devices of the invention is provided with a single, short channel for high frequency gain. The device of the invention is also provided with an asymmetric oxide in the trench gate, as well as LDD regions that lower the gate-drain capacitance for improved RF performance. Such features allow these devices to maintain the advantages of the LDMOS structure (better linearity), thereby increasing the RF power gain. The trench gate LDMOS of the invention also reduces the hot carrier effects when compared to regular LDMOS devices by reducing the peak electric field and impact ionization. Thus, the devices of the invention will have a better breakdown capability.
286 Citations
39 Claims
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1. A method for making a MOSFET, comprising:
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providing a substrate including an epitaxial layer; forming a first trench in the epitaxial layer; filling the first trench with an insulating layer; forming a second trench in the insulating layer such that the second trench is not symmetric relative to the first trench; filling the second trench with a conductive material; and forming a plurality of dopant regions adjacent the first trench with a first one of the plurality of dopant regions extending under the first trench. - View Dependent Claims (2, 3, 4)
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5. A method for making a MOSFET, comprising:
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providing a substrate having an epitaxial layer thereon; forming a first trench in the epitaxial layer; filling the first trench with an oxide layer; forming a second trench in the oxide layer so that the second trench is not symmetric relative to the first trench; filling the second trench with a conductive material; and forming a plurality of dopant regions adjacent the first trench and within the epitaxial layer, wherein the plurality of dopant regions contains a first dopant region extending under the first trench and a second dopant region with a dopant concentration higher than the first dopant region. - View Dependent Claims (6)
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7. A method of forming a MOSFET, comprising:
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forming a first trench in a silicon region extending over a substrate, the silicon region and the substrate being of a first conductivity type but having different doping concentrations; filling the first trench with an insulating layer; forming a second trench in the insulating layer, the second trench being asymmetrical relative to the first trench such that a spacing between a first sidewall of the first trench and a corresponding first sidewall of the second trench is different than a spacing between a second sidewall of the first trench and a corresponding second sidewall of the second trench; forming a conductive material in the second trench; and forming a first drift region of a second conductivity type in the silicon region, the first drift region extending under the first trench. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A MOSFET comprising:
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a first silicon region of a first conductivity type; a gate trench extending into the first silicon region, the gate trench having an asymmetric insulating layer along two of its opposing sidewalls; a source region having a dopant region of a second conductivity type, the dopant region laterally extending along one side of the gate trench to contact a source electrode; and a lightly doped drain region of the second conductivity type laterally extending below and along an opposing side of said one side of the gate trench to contact a drain electrode, wherein a spacing between the drain electrode and the gate trench is greater than a corresponding spacing between the source electrode and the gate trench. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A MOSFET comprising:
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a first silicon region of a first conductivity type; a gate trench extending into the first silicon region, the gate trench having an asymmetric insulating layer along two of its opposing sidewalls; a source region having a dopant region of a second conductivity type, the dopant region laterally extending along one side of the gate trench to contact a source electrode; and a lightly doped drain region of the second conductivity type laterally extending below and along an opposing side of said one side of the gate trench to contact a drain electrode, the lightly doped drain region comprising at least first and second drift regions, the second drift region being laterally separated from the gate trench at least by the first drift region, the first drift region having a lower doping concentration than the second drift region. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A MOSFET comprising:
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an epitaxial layer of a first conductivity type over a substrate; a gate trench extending into the epitaxial layer, the gate trench having an asymmetric insulating layer along two of its opposing sidewalls; a source region having a dopant region of a second conductivity type in the epitaxial layer, the dopant region laterally extending along one side of the gate trench to contact a source electrode; and a lightly doped drain region of the second conductivity type laterally extending below and along an opposing side of said one side of the gate trench to contact a drain electrode, the lightly doped drain region comprising at least first and second drift regions, the second drift region being laterally separated from the gate trench at least by the first drift region, the first drift region having a lower doping concentration than the second drift region, wherein a spacing between the drain electrode and the gate trench is greater than a corresponding spacing between the source electrode and the gate trench. - View Dependent Claims (29, 30, 31)
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32. A MOSFET comprising:
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a first silicon region of a first conductivity type; first and second gate trenches extending into the first silicon region, the first gate trench having an asymmetric insulating layer along two of its opposing sidewalls, the second gate trench having a symmetric insulating layer along two of its opposing sidewalls; a plurality of dopant regions in the first silicon region, a first one of the plurality of dopant regions having a second conductivity type and laterally extending along one side of the second gate trench to contact a source electrode, and a second one of the plurality of dopant regions of the second conductivity type separating the first and second gate trenches; and a lightly doped drain region of the second conductivity type laterally extending along one side of the first gate trench to contact a drain electrode, the lightly doped drain region further extending below both the first and second gate trenches. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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Specification