A transistor's drive current scales with how fast carriers move through its channel, and strain - mechanically stressing the silicon lattice - raises that mobility. Strain engineering has been a foundry workhorse since the 90nm era, so any new strained-channel patent has to claim something specific to survive prior art. Taiwan Semiconductor Manufacturing Co., Ltd.'s end-of-2020 grant, authored by its prolific SRAM and cell-design inventor Jhon Jhy Liaw, does exactly that.
US10861936B2, "Fin-like field effect transistors having high mobility strained channels and methods of fabrication thereof" (issued 2020-12-08), is classified in H01L 29/1054 (high-mobility channel regions) with H01L 29/785 (FinFET) and a chain of fabrication subclasses. The claim is not on 'a strained channel' but on a specific high-mobility channel material and the method that produces the strain.
“Fin-like field effect transistors (FinFETs) having high mobility strained channels and methods of fabrication thereof are disclosed herein. An exemplary method includes forming a first silicon fin in a first type FinFET device region and a second silicon fin in a second type FinFET device region.”— U.S. Patent No. 10,861,936 source
Construe the channel limitation. The value is in which material system the claim requires - typically a SiGe or Ge-rich channel for PMOS mobility, or a tensile-strained Si channel for NMOS - and the formation sequence that achieves and preserves that strain through the rest of the flow. Strain that relaxes during subsequent thermal steps is worthless, so the method matters.
The design-around space is genuinely large here, because there are many ways to strain a channel: stressor liners, embedded source/drain epitaxy, substrate engineering, and channel material choice. A competitor using a different strain source reaches similar mobility without infringing a claim tied to one specific scheme.
That breadth of alternatives is why this kind of patent functions more as portfolio depth than as a blocking claim. It adds to TSMC's count in the FinFET channel-engineering space - where the facet data shows TSMC and IBM dominating - rather than walling off a chokepoint.
For a claim-construction read, the lesson is to resist the title's generality. 'High-mobility strained channel' sounds broad; the independent claim almost certainly narrows to one material-and-method combination, and that combination is the only thing actually fenced.