LOCOS with sidewall spacer for transistors and other devices
An integrated circuit (IC) includes a first field-plated field effect transistor (FET), and a second field-plated FET, and functional circuitry configured together with the field-plated FETs for realizing at least one circuit function in a semiconductor surface layer on a substrate. The field-plated FETs include a gate structure including a gate electrode partially over a LOCOS field relief oxide and partially over a gate dielectric layer. The LOCOS field relief oxide thickness for the first field-plated FET is thicker than the LOCOS field relief oxide thickness for the second field-plated FET. There are sources and drains on respective sides of the gate structures in the semiconductor surface layer.
1. An integrated circuit (IC), comprising:
a first field-plated field effect transistor (FET) having a first gate structure including a first gate electrode partially over a first field relief oxide and partially over a gate dielectric layer; and
a second field-plated FET having a second gate structure including a second gate electrode partially over a second field relief oxide and partially over the gate dielectric layer, wherein:
a first thickness of the first field relief oxide for the first field-plated FET is thicker than a second thickness of the second field relief oxide for the second field-plated FET;
the first field relief oxide has first tapered edges, a center portion of the first thickness, and an intermediate portion between opposite edges of the first tapered edges and the center portion, the intermediate portion having a third thickness of the first field relief oxide that is less than the first thickness; and
the second field relief oxide has second tapered edges and a top surface between the second tapered edges that is flat.
2. The IC of claim 1 , wherein the second thickness of the second field relief oxide is 200 to 1,000 Å, and wherein the first thickness for the first field relief oxide is at least 500 Å thicker than the second thickness for the second field relief oxide.
3. The IC of claim 1 , wherein a semiconductor surface layer is recessed under the first field relief oxide and the second field relief oxide.
4. The IC of claim 1 , wherein the first thickness for the first field relief oxide is at least 500 Å thicker than the second thickness for the second field relief oxide.
5. The IC of claim 1 , wherein the first field-plated FET and the second field plated FET each comprise a laterally diffused metal oxide semiconductor (LDMOS) device.
6. The IC of claim 1 , wherein the gate electrode comprises polysilicon.
7. The IC of claim 1 , wherein a thickness of the gate dielectric layer is less than half the second thickness of the second field relief oxide.
8. The IC of claim 1 , wherein the first and second field-plated FETs each comprise a n-channel laterally diffused metal oxide semiconductor (LDMOS) device.
9. The IC of claim 1 , wherein a source of the first field-plated FET and a source of the second field-plated FET are both connected to a ground node on the IC to be configured as power diodes.
10. The IC of claim 1 , wherein both the first thickness and the third thickness are greater than the second thickness of the second field relief oxide.
11. An integrated circuit (IC), comprising:
a first field-plated field effect transistor (FET) comprising a first gate structure including a first gate electrode partially over a first field relief oxide and partially over a first gate dielectric layer;
a second field-plated FET comprising a second gate structure including a second gate electrode partially over a second field relief oxide and partially over a second gate dielectric layer; and
sources and drains on respective sides of the first and second gate structures in a semiconductor surface layer; wherein:
a first thickness of the first field relief oxide for the first field-plated FET is thicker than a second thickness of the second field relief oxide for the second field-plated FET,
the first field relief oxide has first and second tapered edges, a center portion of the first thickness, and an intermediate portion between each of the first and second tapered edges and the center portion, the intermediate portion having a third thickness of the first field relief oxide that is less than the first thickness and greater than the second thickness; and
the semiconductor surface layer is recessed under the first field relief oxide for the first field-plated FET and under the second field relief oxide for the second field-plated FET.
12. The IC of claim 11 , wherein the second thickness of the second field relief oxide for the second field-plated FET is 200 to 1,000 Å, and wherein the first thickness for the first field relief oxide for the first field-plated FET is at least 500 Å thicker than the second thickness for the second field relief oxide for the second field-plated FET.
13. The IC of claim 11 , wherein the first and second field-plated FETs comprise laterally diffused metal oxide semiconductor (LDMOS) devices.
14. The IC of claim 11 , wherein a width of the first field relief oxide for the first field-plated FET is at least 0.05 μm greater than a width of the second field relief oxide for the second field-plated FET.
15. The IC of claim 11 , wherein the first gate electrode comprises polysilicon.
16. The IC of claim 11 , wherein the semiconductor surface layer comprises an epitaxial layer.
17. An integrated circuit (IC), comprising:
a first field-plated field effect transistor (FET) comprising a first gate structure including a first gate electrode partially over a first field relief oxide and partially over a first gate dielectric layer;
a second field-plated FET comprising a second gate structure including a second gate electrode partially over a second field relief oxide and partially over a second gate dielectric layer; and
sources and drains on respective sides of the first and second gate structures in a semiconductor surface layer; wherein:
a first thickness of the first field relief oxide for the first field-plated FET is thicker than a second thickness of the second field relief oxide for the second field-plated FET,
the first field relief oxide has first and second tapered edges, a center portion of the first thickness, and an intermediate portion between each of the first and second tapered edges and the center portion, the intermediate portion having a third thickness of the first field relief oxide that is less than the first thickness and greater than the second thickness, and
the thickness of the first and second field relief oxides are both at least twice as thick as the first and second gate dielectric layers.
18. The IC of claim 11 , wherein the first and second field-plated FETs each comprise n-channel laterally diffused metal oxide semiconductor (LDMOS) devices.
19. An integrated circuit (IC), comprising:
a first field-plated field effect transistor (FET) having a first gate structure including a first gate electrode partially over a first field relief oxide and partially over a gate dielectric layer, wherein the first field relief oxide has first end portion, a second end portion, a center portion of a first thickness, and an intermediate portion of a second thickness less than the first thickness, the intermediate portion located between the center portion and both the first end portion and the second end portion; and
a second field-plated FET having a second gate structure including a second gate electrode partially over a second field relief oxide and partially over the gate dielectric layer, wherein the first and second thicknesses of the first field relief oxide for the first field-plated FET are thicker than a thickness of the second field relief oxide for the second field-plated FET.