IP Law Daily, PATENT—N.D. Cal.: Accused products do not infringe, based on plain meaning of ‘and’, (Apr 14, 2026)

By Anne H. Gibson, J.D., LL.M.

Dispute between semiconductor manufacturers continues with other infringement claims.

In a patent dispute between semiconductor manufacturers, one asserted patent was not infringed by the accused products because they did not meet the requirements of the patent, the federal district court in San Jose, California, has held. The court found that the word “and” in the relevant claim required both of two conditions to be met, not just one of the two. Patent owner Force MOS Technology Co., Ltd. (Force MOS) and Alpha and Omega Semiconductor Ltd. (AOS)—which both produce metal oxide semiconductor field effect transistors (MOSFETs)—filed dueling motions for summary judgment, as well as motions to strike certain evidence and information. The motions were granted in part and denied in part. Two other asserted patents were not affected by the ruling, and infringement contentions against AOS regarding them remain pending (Alpha and Omega Semiconductor Ltd. v. Force MOS Technology Co., Ltd., No. 5:22-cv-05448-PCP (N.D. Cal. Apr. 13, 2026)).

Patents-in-suit. Patent owner Force MOS produces MOSFETs. It holds three patents related to power MOSFETs, which “are designed to handle significant current and voltage and, like other transistors, have three electrical leads or terminals: a source, a drain, and a gate.” The three patents, U.S. Patent No. 7,629,634 (’634 patent), U.S. Patent No. 7,847,346 (’346 patent), and U.S. Patent No. 7,646,058 (’058 patent) are related to trench MOSFETs, a type of power MOSFET. The ‘058 patent, at issue in the summary judgment motions, seeks to improve the heat dissipation of trenched MOSFETs. Force MOS has sold MOSFETs using these parents since 2017.

Infringement dispute. AOS also produces MOSFETs. In September 2022, Force MOS sent a letter asserting that AOS’s products infringed on the ‘634 patent. AOS then filed a motion for declaratory judgment that its products do not do so. Force MOS subsequently accused AOS of infringing on the ‘346 patent and the ‘058 patent. AOS amended its complaint to pertain to these patents as well, and Force MOS filed counterclaims against AOS and its subsidiary Jireh.

AOS moved for summary judgment as to Force MOS’s patent infringement claim regarding the ‘058 patent and as to its marking defense to Force MOS’s claims against it. Force MOS moved for summary judgment as to the marking defense, and it moved to strike or exclude certain evidence and related expert testimony.

Infringement of ‘058 patent. AOS argued that the undisputed facts on the record indicate that its products do not infringe on the ‘058 patent. The ‘058 patent pertains to a trench MOSFET that contains metallic contact plugs and a solderable front metal. Claim 1 of the ’058 patent requires that “said metallic contact plugs and said front metal are composed of a metallic material having a thermal conductivity higher than a thermal conductivity of aluminum and/or aluminum alloys.” The court noted that AOS’s accused products contained “metallic contact plugs composed of tungsten, which has a lower thermal conductivity than aluminum.” AOS argued that, since its metallic contact plugs do not meet the specification of claim 1, its products could not have infringed the ‘058 patent.

Force MOS argued that the “and” in claim 1 was ambiguous and was disjunctive in this case, meaning it meant “or” and that, therefore, a product with metallic contact plugs OR front metal with a thermal conductivity higher than aluminum would infringe on the patent.

The court disagreed. “In this case, ‘and’ unambiguously means ‘and,’” the court said. The court considered Force MOS’s arguments to the contrary, but rejected them. It cited Lucent Techs., Inc. v. Gateway, Inc., 525 F.3d 1200 (Fed. Cir. 2008), for the prospect that “courts may not redraft claims to cure a drafting error made by the patentee, whether to make them operable or to sustain their validity.” It found that the meaning of the claim was unambiguous and that it was undisputed that AOS’s products did not match the specifications. AOS’s motion for summary judgment that its products did not infringe the ‘058 patent was granted.

Marking defense. The court next turned to the parties’ dueling summary judgment motions as to AOS and Jireh’s marking defense. AOS and Jireh asserted that Force MOS had failed to mark its products that were sold in the United States prior to 2024, and therefore could not recover damages prior to that date, under 35 U.S.C. § 287(a). Force MOS also moved for summary judgment on this claim, arguing that AOS and Jireh had not met their burden in articulating the products that they were asserting were unmarked.

The court found that AOS and Jireh did not meet their burden. “AOS never specifically identified the Force MOS products that it believes practiced the asserted patents, were made or sold in the United States, and were unmarked prior to the dates on which AOS received actual notice of its alleged infringement,” the court explained. Consequently, the court granted Force MOS’s motion for summary judgment on AOS and Jireh’s marking defenses.

Motions to strike evidence and expert testimony. Force MOS made motions to strike certain evidence and information, as well as AOS’s expert testimony related to them: (1) “ship-and-debit credits” related to AOS’s revenue from sales of accused products; (2) documents regarding the composition of AOS’s soldering pastes; (3) an agreement AOS used to estimate royalty rates (the Cerian Agreement); and (4) purportedly non-infringing alternatives.

The court noted that “Rule 37(c)(1) prohibits a party from using evidence or information at trial if the party failed to disclose it ‘as required by Rule 26(a) or (e) …, unless the failure was substantially justified or harmless.’” Force MOS argued that AOS had not timely disclosed the four items of evidence and information at issue.

In short, the court agreed with Force MOS as to the “ship-and-debit credits” and the Cerian Agreement. These were available to AOS at the fact disclosure stage, but were not produced until much later in the proceedings. Consequently, the motion to strike these documents and related expert testimony was granted.

The documents related to soldering pastes were relevant only to the ‘058 patent claims, and so that motion to strike was found moot.

Finally, although the court agreed that AOS should have provided the information about purportedly non-infringing alternatives earlier, the error was “harmless.” It found that Force MOS had an opportunity to address the alternatives, which cured the deficiency. The court thus denied the motion to strike the non-infringing alternatives.

The Case is No. 5:22-cv-05448-PCP.

Judge: Pitts, P.

Attorneys: Mario Moore (Dan Johnson Law Group, LLP) for Alpha and Omega Semiconductor Ltd. Christopher Hanba (Prince Lobel Tye LLP) for Force MOS Technology Co., Ltd.

Companies: Alpha and Omega Semiconductor Ltd.; Force MOS Technology Co., Ltd.

Cases: Patent CaliforniaNews