| US 7,615,425 B2 | ||
| Open source/drain junction field effect transistor | ||
| Joe R. Trogolo, Plano, Tex. (US); Hiroshi Yasuda, Dallas, Tex. (US); Badih El-Kareh, Cedar Park, Tex. (US); and Philipp Steinmann, Richardson, Tex. (US) | ||
| Assigned to Texas Instruments Incorporated, Dallas, Tex. (US) | ||
| Filed on Aug. 15, 2006, as Appl. No. 11/504,412. | ||
| Prior Publication US 2008/0042199 A1, Feb. 21, 2008 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. H01L 21/337 (2006.01) | ||
| U.S. Cl. 438—186 [257/256] | 26 Claims |

| 1. A method of forming a p type junction field effect transistor and an n type junction field effect transistor in a semiconductor
substrate, comprising:
forming a first n type buried layer in the substrate;
forming a first p type buried layer in the substrate;
forming a first n type epitaxial layer over the substrate;
forming a second p type buried layer over the first p type buried layer in the first n type epitaxial layer;
forming one or more deep n+ type regions over at least some of the first n type buried layer in the first n type epitaxial
layer;
forming a second n type epitaxial layer over the first n type epitaxial layer;
forming a p type surface shield near an upper surface of the second n type epitaxial layer, where the p type surface shield
resides over at least some of the second p type buried layer;
forming an n type channel in the second n type epitaxial layer, where the n type channel resides over at least some of the
second p type buried layer;
forming a p type back gate extension near a lower surface of the second n type epitaxial layer, where the p type back gate
extension resides over at least some of the second p type buried layer and over less than all of the first n type buried layer;
forming an n type surface shield near an upper surface of the second n type epitaxial layer, where the n type surface shield
resides over at least some of the first n type buried layer;
forming a p type channel in the second n type epitaxial layer, where the p type channel resides over at least some of the
first n type buried layer;
forming one or more isolation areas that isolate the p type junction field effect transistor from the n type junction field
effect transistor;
forming one or more n type deep back gate contact regions in the second n type epitaxial layer down to the one or more deep
n+ type regions in the p type junction field effect transistor;
forming one or more p type deep back gate contact regions in the second n type epitaxial layer down to the second p type buried
layer in the n type junction field effect transistor;
forming a deep p type region in the second n type epitaxial layer down to the second p type buried layer in the p type junction
field effect transistor:
forming a layer of silicide block material over the second n type epitaxial layer;
patterning the silicide block material to expose areas of the second n type epitaxial layer where gate, source and drain regions
are to be formed;
forming an n type gate region in the p type channel of the p type junction field effect transistor, and n type source and
drain regions in the n type channel of the n type junction field effect transistor;
forming p type source and drain regions in the p type channel of the p type junction field effect transistor, and a p type
gate region in the n type channel of the n type junction field effect transistor;
siliciding the gate, source and drain regions in the p type channel of the p type junction field effect transistor and the
n type channel of the n type junction field effect transistor;
forming a layer of dielectric material over the silicides and second n type epitaxial layer;
forming conductive contacts down through the layer of dielectric material to the silicided gate, source and drain regions
in the p type channel of the p type junction field effect transistor and the n type channel of the n type junction field effect
transistor; and
forming a field plate over at least one of the conductive contacts extending down to the gate regions of the p type junction
field effect transistor and the n type junction field effect transistor, where the field plates also extend over at least
some of at least one of the source and drain regions of the p type junction field effect transistor and the source and drain
regions of the n type junction field effect transistor.
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