Metal-oxide-semiconductor device having improved performance and reliability
A method for forming a MOS device includes the steps of forming a gate proximate an upper surface of a semiconductor layer, the semiconductor layer including a substrate of a first conductivity type and a second layer of a second conductivity type; forming first and second source/drain regions of the second conductivity type in the second layer proximate the upper surface of the second layer, the first source/drain region being spaced laterally from the second source/drain region, the gate being formed at least partially between the first and second source/drain regions; and forming at least one electrically conductive trench in the second layer between the gate and the second source/drain region, the trench being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate. The step of forming the trench includes the steps of forming an insulating layer substantially lining sidewalls of the trench, and substantially filling the trench with an electrically conductive material.
1. A method for forming a metal-oxide-semiconductor (MOS) device, comprising the steps of:
forming a gate proximate an upper surface of a semiconductor layer, the semiconductor layer comprising a substrate of a first conductivity type and a second layer of a second conductivity type;
forming first and second source/drain regions of the second conductivity type in the second layer proximate the upper surface of the second layer, the first source/drain region being spaced laterally from the second source/drain region, the gate being formed at least partially between the first and second source/drain regions; and
forming at least one electrically conductive trench in the second layer between the gate and the second source/drain region, the at least one trench being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate;
wherein the step of forming the at least one trench comprises the steps of forming an insulating layer substantially lining sidewalls of the trench, and substantially filling the trench with an electrically conductive material.
2. The method of claim 1 , wherein the at least one trench is configured such that as a voltage at the second source/drain region increases, a depletion region spreads from the trench to substantially fill a region proximate the trench, thereby reducing hot carrier injection in the device.
3. The method of claim 1 , further comprising the step of forming a second electrically conductive trench in the second layer between the gate and the second source/drain region, the second trench being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate, the at least first and second trenches being spaced apart relative to one another and configured such that as a voltage at the second source/drain region increases, a depletion region spreads from the trenches to substantially fill a region between the trenches, thereby reducing hot carrier injection in the device.
4. The method of claim 1 , further comprising the step of forming a shielding structure proximate the upper surface of the semiconductor layer and between the gate and the second source/drain region, the shielding structure being electrically connected to the first source/drain region, the shielding structure being spaced laterally from the gate and being substantially non-overlapping relative to the gate.
5. The method of claim 4 , wherein the at least one trench is formed proximate the shielding structure.
6. The method of claim 1 , wherein the second layer comprises an epitaxial layer.
7. The method of claim 1 , wherein the insulating material comprises an oxide and the electrically conductive material comprises polysilicon.
8. The method of claim 1 , wherein the device comprises a diffused MOS (DMOS) device.
9. The method of claim 1 , wherein the device comprises a lateral DMOS (LDMOS) device.
10. The method of claim 1 , wherein the first source/drain region comprises a source region and the second source/drain region comprises a drain region.
11. The method of claim 1 , wherein the step of forming the at least one trench comprises forming a v-groove in the second layer between the gate and the second source/drain region.
12. The method of claim 1 , wherein the step of forming the at least one trench comprises forming a diffused sinker in the second layer between the gate and the second source/drain region.
13. The method of claim 1 , further comprising the step of forming a plurality of electrically conductive trenches in the second layer between the gate and the second source/drain region, the trenches being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate, the trenches being spaced apart relative to one another and configured such that as a voltage at the second source/drain region increases, a depletion region spreads from the trenches to substantially fill a region between the trenches, thereby reducing hot carrier injection in the device.
14. The method of claim 13 , wherein the trenches are spaced apart relative to one another and distributed substantially uniformly throughout a region between the gate and second source/drain region.
15. A method for forming an integrated circuit (IC) device comprising one or more metal-oxide semiconductor (MOS) devices, the method comprising the steps of:
forming a gate proximate an upper surface of a semiconductor layer, the semiconductor layer comprising a substrate of a first conductivity type and a second layer of a second conductivity type;
forming first and second source/drain regions of the second conductivity type in the second layer proximate the upper surface of the second layer, the first source/drain region being spaced laterally from the second source/drain region, the gate being formed at least partially between the first and second source/drain regions; and
forming at least one electrically conductive trench in the second layer between the gate and the second source/drain region, the at least one trench being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate;
wherein the step of forming the at least one trench comprises the steps of forming an insulating layer substantially lining sidewalls of the trench, and substantially filling the trench with an electrically conductive material.
16. The method of claim 15 , wherein the at least one trench is configured such that as a voltage at the second source/drain region increases, a depletion region spreads from the trench to substantially fill a region proximate the trench, thereby reducing hot carrier injection in the device.
17. The method of claim 15 , further comprising the step of forming a second electrically conductive trench in the second layer between the gate and the second source/drain region, the second trench being formed proximate the upper surface of the semiconductor layer and extending substantially vertically through the second layer to the substrate, the at least first and second trenches being spaced apart relative to one another and configured such that as a voltage at the second source/drain region increases, a depletion region spreads from the trenches to substantially fill a region between the trenches, thereby reducing hot carrier injection in the device.
18. The method of claim 15 , further comprising the step of forming a shielding structure proximate the upper surface of the semiconductor layer and between the gate and the second source/drain region, the shielding structure being electrically connected to the first source/drain region, the shielding structure being spaced laterally from the gate and being substantially non-overlapping relative to the gate.