DCT
3:25-cv-09240
Qorvo Inc v. Denso Corp
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Qorvo, Inc. (Delaware)
- Defendant: Denso Corporation (Japan); National Institute of Advanced Industrial Science and Technology (AIST) (Japan)
- Plaintiff’s Counsel: Alston & Bird LLP
- Case Identification: 3:25-cv-09240, N.D. Cal., 10/27/2025
- Venue Allegations: Plaintiff Qorvo alleges venue is proper in the Northern District of California because the Defendants are foreign entities and because a substantial part of the events giving rise to the action, including infringement allegations and in-person meetings, occurred within the district.
- Core Dispute: Plaintiff seeks a declaratory judgment that its bulk acoustic wave (BAW) filter products do not infringe two of Defendants' patents, which relate to the specific atomic composition of piezoelectric thin films.
- Technical Context: The technology at issue is scandium aluminum nitride (ScAlN), a piezoelectric material used to create high-frequency radio frequency (RF) filters that are essential components in modern wireless communication devices.
- Key Procedural History: The complaint details a nearly two-year history of pre-suit correspondence and meetings initiated by a November 2023 letter from Denso alleging infringement of the '979 patent. The dispute later expanded to include the '342 patent. During these discussions, Qorvo alleges that Denso acknowledged errors in its initial product testing but maintained its infringement position. The complaint also notes that Denso filed a lawsuit against a third party, Skyworks Solutions, on the '979 patent in June 2025. For the '342 patent, the complaint highlights that the applicant added a lower limit for carbon content during prosecution to overcome prior art, an event that may be significant for determining the patent's claim scope.
Case Timeline
| Date | Event |
|---|---|
| 2007-05-31 | U.S. Patent No. 7,758,979 Priority Date |
| 2010-07-20 | U.S. Patent No. 7,758,979 Issued |
| 2013-05-31 | U.S. Patent No. 9,735,342 Priority Date |
| 2017-08-15 | U.S. Patent No. 9,735,342 Issued |
| 2023-11-29 | Denso sends letter to Qorvo alleging infringement of the '979 patent |
| 2024-07-25 | Denso expands allegations to include the '342 patent |
| 2025-06-20 | Denso files suit against Skyworks Solutions on the '979 patent |
| 2025-10-27 | Qorvo files Complaint for Declaratory Judgment |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,758,979 - "Piezoelectric thin film, piezoelectric materials, and fabrication method of piezoelectric thin film and piezoelectric material, and piezoelectric resonator, actuator element, and physical sensor using piezoelectric thin film," Issued July 20, 2010
The Invention Explained
- Problem Addressed: The patent's background section explains that while aluminum nitride (AlN) is a preferable material for high-frequency RF filters due to its favorable physical properties, it suffers from a low "piezoelectric constant." This limitation requires higher operating voltages, making devices less power-efficient and limiting performance improvements (Compl. ¶32; ’979 Patent, col. 1:41-51).
- The Patented Solution: The invention introduces a specific amount of scandium (Sc) into the aluminum nitride film. This addition is described as varying the material's crystal structure to significantly improve its piezoelectric response, allowing for more efficient conversion of electrical signals to mechanical vibrations, while preserving the other desirable characteristics of AlN (’979 Patent, Abstract; col. 3:5-9).
- Technical Importance: This improved material enables the design of smaller, more power-efficient, and higher-performance RF filters and resonators, which are critical for advancing portable electronic devices like mobile phones (’979 Patent, col. 3:51-63).
Key Claims at a Glance
- The complaint asserts non-infringement of independent claim 6 (Compl. ¶¶39, 45).
- Claim 6 requires:
- A piezoelectric thin film comprising an aluminum nitride thin film containing scandium,
- wherein a content ratio of the scandium is in a range of 10 atom % to 35 atom % or 40 atom % to 50 atom %,
- based on the assumption that the total atoms of scandium and aluminum in the film is 100 atom %.
U.S. Patent No. 9,735,342 - "Piezoelectric thin film and method for producing the same," Issued August 15, 2017
The Invention Explained
- Problem Addressed: The patent identifies that scandium aluminum nitride films produced via sputtering—a common manufacturing technique—can exhibit inconsistent piezoelectric properties. The inventors determined that contamination by carbon atoms during the manufacturing process was a cause of this performance deterioration (’342 Patent, col. 5:36-44).
- The Patented Solution: The invention is a ScAlN piezoelectric thin film where the carbon atomic content is specifically controlled to be within a low, defined range (2.5 at % or less). By controlling this impurity, the film can reliably achieve "excellent piezoelectric properties" comparable to a pure film without carbon contamination (’342 Patent, Abstract; col. 5:55-63). The patent describes achieving this by using a sputtering target material with a low carbon content (’342 Patent, col. 6:1-5).
- Technical Importance: Controlling for carbon impurities provides a method for reliably and consistently mass-producing high-performance ScAlN films, a key requirement for commercial-scale manufacturing of RF components (’342 Patent, col. 5:55-63).
Key Claims at a Glance
- The complaint asserts non-infringement of independent claim 1 (Compl. ¶¶47, 54).
- Claim 1 requires:
- A piezoelectric thin film formed through sputtering that consists essentially of scandium aluminum nitride,
- wherein the film has a carbon atomic content between 0.1 at % and 2.5 at %.
III. The Accused Instrumentality
Product Identification
- The complaint identifies two categories of Qorvo's bulk acoustic wave (BAW) filters (Compl. ¶¶39, 47).
- Accused Scandium Products: A group of filters, including models EG2516, EG2538, and EG9128, alleged by Denso to infringe the ’979 Patent (Compl. ¶39).
- Accused Carbonless Products: A separate group of filters, including models EG2625 and EG2812, alleged by Denso to infringe the ’342 Patent (Compl. ¶47, p. 8:1-2).
Functionality and Market Context
- These products are semiconductor components used for RF signal filtering in a wide range of high-growth markets, including consumer electronics and network infrastructure (Compl. ¶¶4, 8). The complaint alleges these filters are manufactured using ScAlN films whose specific atomic compositions are central to the dispute.
- For the Accused Scandium Products, the complaint alleges they are designed to have scandium content below the 10 atom % lower limit of the ’979 Patent's asserted claim, with specific product families having 6.4±0.3 atom % or 9.5±0.3 atom % scandium (Compl. ¶¶41-43).
- For the Accused Carbonless Products, the complaint alleges they contain a maximum carbon content of 0.027 atomic %, which is less than the 0.1 atom % lower limit of the ’342 Patent's asserted claim (Compl. ¶¶49-50).
No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
This is a declaratory judgment action for non-infringement. The tables below summarize Qorvo's asserted non-infringing functionality against the claim elements Denso has allegedly asserted.
’979 Patent Infringement Allegations
| Claim Element (from Independent Claim 6) | Asserted Non-Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a content ratio of the scandium being in a range of 10 atom % to 35 atom % or 40 atom % to 50 atom % | Qorvo asserts its products are designed with scandium content below the claimed 10 atom % lower bound. Specifically, certain filters allegedly contain 6.4±0.3 atom % scandium, while others contain 9.5±0.3 atom % scandium. | ¶¶42-43 | col. 22:26-28 |
’342 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Asserted Non-Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| the piezoelectric thin film has a carbon atomic content between 0.1 at % and 2.5 at % | Qorvo asserts its products are designed with a carbon atomic content of less than the claimed 0.1 at % lower bound, with an alleged maximum content of 0.027 atomic %. | ¶¶49-50 | col. 9:27-28 |
Identified Points of Contention
- Evidentiary Questions: The central dispute appears to be factual and evidentiary: What are the true, measurable atomic compositions of Qorvo's accused filters? The complaint raises questions about the reliability of Denso's testing methods and suggests a fundamental factual disagreement over the products' material makeup (Compl. ¶¶11, 14).
- Legal Questions: Should the factual dispute be resolved in Qorvo's favor, the case may turn on the doctrine of equivalents. A key question for the '979 patent will be whether a product with scandium content just below the claimed 10% threshold is legally equivalent. For the '342 patent, a primary legal question will be whether prosecution history estoppel bars any assertion of equivalence for products with carbon content below the 0.1% limit that was added to overcome prior art (Compl. ¶51).
V. Key Claim Terms for Construction
For the ’979 Patent
- The Term: "a content ratio of the scandium being in a range of 10 atom % to 35 atom %"
- Context and Importance: This numerical range is the basis of Qorvo's non-infringement argument. The case will depend on whether this 10% value is a strict, literal boundary or if compositions falling just outside it could still be found to infringe.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent specification discloses a broader inventive range of 0.5 atom % to 50 atom % scandium for improving piezoelectric response, which could be used to argue that the claimed range is not a rigid cliff (’979 Patent, col. 3:34-40).
- Evidence for a Narrower Interpretation: Claim 6 recites the "10 atom %" value explicitly and without qualification. Patent figures, such as FIG. 1, appear to show a distinct performance curve where piezoelectric response rises significantly around and above this 10% mark, suggesting the inventors identified a specific technical threshold (’979 Patent, Fig. 1).
For the ’342 Patent
- The Term: "a carbon atomic content between 0.1 at % and 2.5 at %"
- Context and Importance: This range is dispositive, as Qorvo alleges its products fall below the 0.1% lower bound. Practitioners may focus on this term because its lower limit was added during prosecution to secure the patent.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent's overall objective is to minimize carbon contamination. Denso could argue that the invention covers any film where carbon is present but controlled to a low level to achieve high performance.
- Evidence for a Narrower Interpretation: The complaint alleges that the applicant added the "0.1 at %" lower limit specifically to distinguish the invention from prior art that disclosed films with "less than 0.1 wt% of various impurities" (Compl. ¶51). This prosecution history may create a strong estoppel, preventing Denso from arguing that products with less than 0.1 at % carbon infringe, either literally or under the doctrine of equivalents.
VI. Other Allegations
- Indirect Infringement: The complaint states that Qorvo's products do not infringe "either directly or indirectly," but does not provide sufficient detail for analysis of any specific theory of induced or contributory infringement that Denso may have alleged (Compl. ¶¶40, 48).
VII. Analyst’s Conclusion: Key Questions for the Case
This case appears to center on highly technical, factual measurements of material science, with significant legal implications related to claim scope. The key questions for the court will likely be:
A central issue will be one of evidentiary proof: What are the actual, verifiable atomic percentages of scandium and carbon in Qorvo's accused filter products? The resolution of this factual question will determine whether there is any literal infringement.
A critical legal issue for the '342 patent will be the effect of prosecution history estoppel: Did the patent owner, by adding a 0.1 at % lower carbon limit to overcome prior art, permanently surrender the right to claim infringement by any product—including under the doctrine of equivalents—that falls below this specific numerical threshold?
If literal infringement is not found for the '979 patent, a key question will be the application of the doctrine of equivalents: Does a ScAlN film with scandium content just below the claimed 10% lower limit perform substantially the same function, in substantially the same way, to achieve substantially the same result as the patented invention, or does the claim's numerical boundary represent a non-equivalent, patentable distinction?