Silicide block isolation for reducing off-capacitance of a radio frequency (RF) switch
A silicon-on-insulator (SOI) CMOS transistor structure includes a plurality of series-connected SOI CMOS transistors, including a plurality of parallel source/drain regions, a plurality of channel/body regions located between the plurality of source/drain regions, and a polysilicon gate structure located over the plurality of channel regions. The polysilicon gate structure includes a plurality of polysilicon gate fingers, wherein each polysilicon gate finger extends over a corresponding one of the channel/body regions. A silicide blocking structure is formed over portions of the polysilicon gate fingers, wherein channel/body contact regions, which extend at least partially under the silicide blocking structure, provide electrical connections to the parallel channel/body regions.
1. A method comprising:
forming a plurality of polysilicon gate electrodes over an active region of a silicon-on-insulator structure;
forming a plurality of source/drain regions having a first conductivity type in the active region, wherein a plurality of channel/body regions having a second conductivity type exist in the active region, wherein each of the plurality of channel/body regions is located under a corresponding one of the polysilicon gate electrodes, and wherein each of the plurality of channel/body regions is located between adjacent pairs of the plurality of source/drain regions;
forming a first plurality of contact regions having the second conductivity type, wherein the first plurality of contact regions are continuous with first ends of the plurality of channel/body regions, wherein the plurality of polysilicon gate electrode extends between the first plurality of contact regions; then
forming a silicide blocking structure that covers first portions of the first plurality of contact regions, adjacent first portions of the source/drain regions, and first portions of each of the plurality of polysilicon gate electrodes; and then
forming metal silicide regions over portions of the plurality of source/drain regions, portions of the first plurality of contact regions and portions of the polysilicon gate electrodes that are not covered by the silicide blocking structure.
2. The method of claim 1 , further comprising forming a second plurality of contact regions having the second conductivity type, wherein the second plurality of contact regions are continuous with second ends of the plurality of channel/body regions, wherein the first ends and the second ends of the plurality of channel/body regions are opposite ends of the channel/body regions.
3. The method of claim 2 , further comprising forming a second silicide blocking structure that covers first portions of the second plurality of contact regions, adjacent second portions of the source/drain regions, and second portions of each of the plurality of polysilicon gate electrodes.
4. The method of claim 3 , further comprising forming metal silicide regions over portions of the second plurality of contact regions and portions of the polysilicon gate electrodes that are not covered by the second silicide blocking structure.
5. The method of claim 1 , further comprising forming an isolation structure that laterally surrounds the active region.
6. The method of claim 1 , wherein the first portions of the plurality of source/drain regions abut the first portions of the first plurality of contact regions.
7. The method of claim 1 , wherein portions of the plurality of channel/body regions are located between the plurality of source/drain regions and the first plurality of contact regions.
8. The method of claim 1 , further comprising forming one or more of the first plurality of contact regions between the polysilicon gate electrodes.