Invalidity dossier
US 8421195
Semiconductor devices with graded dopant regions
Current assignee: GREENTHREAD LLC
Added 9/23/2026, 11:54:14 AM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US8421195B2
Title: Semiconductor devices with graded dopant regions
Patent number / application: US8421195B2; Application US11/622,496
Inventor: G. R. Mohan Rao
Current assignee (per source): GREENTHREAD LLC (original assignee: Individual)
Key dates (as listed): Priority date 2004-09-03; filing date 2007-01-12; publication of US20070158790A1 on 2007-07-12; granted/publication of US8421195B2 on 2013-04-16; anticipated expiration 2024-09-03; status "Expired - Fee Related."
Stated purpose (source "Definitions" section): The invention "relates to all semiconductor devices and systems." It is said to apply particularly to "diffused diodes, avalanche diodes, Schottky devices, power MOS transistors, JFET's, RF bipolar transistors, IGBTs (Insulated Gate Bipolar Transistors), varactors, digital VLSI, mixed signal circuits and sensor devices including camera ICs" using CCD as well as CMOS technologies. The focus is on graded dopant regions, including an "aiding drift field" in graded base transistors to speed minority carrier transit from emitter to collector; FIG. 1 is described as showing relative doping concentration versus distance in a BJT.
Plain-language scope (from the supplied excerpt): The patent concerns controlling how dopant concentration varies with distance inside semiconductor regions to improve device operation. In bipolar transistors, a graded base can create a built-in field that helps carriers move faster; the excerpt notes that BJTs depend on both electrons and holes, are limited by base transit time and carrier recombination at switch-off, and that diffusion (not drift) dominates current in uniformly doped bases.
Source: https://patents.google.com/patent/[US8421195](/patent/US8421195)/en
What the excerpt does not establish: It provides no claims text, so the actual claimed scope, dependency, and limitations are unknown. It also does not establish the full specification, embodiments, figures (only FIG. 1 is referenced), examples, or any litigation, ownership transfers, validity, or prior-art analysis.
Generated 10/1/2026, 9:53:52 PM
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Litigation summary
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Proceedings on file (0)
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PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
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Obviousness
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Extensions
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Derivative works
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