Narrow Structural Amendment Precludes Equivalents, Regardless of Whether Specifically Required to Overcome Rejection

In Int'l Rectifier Corp. v. IXYS Corp., the Federal Circuit held that prosecution history estoppel barrred IR from asserting infringement of the "adjoining" limitation under the doctrine of equivalents for the following amendments:

[. . . a drain conductive region remote from said common region and separated
therefrom by said relatively lightly doped major body portion;]

said wafer including a further region of opposite conductivity type adjoining said
lightly doped major body portion; and an electrode coupled to said further region

[having a support body for supporting said lightly doped major body portion; said support body being of said opposite conductivity type; and a conductive electrode formed on the surface of said support body disposed opposite to said lightly doped major body portion; said conductive electrode coupled to said drain conductive region.]

According to Circuit Judge Linn,

As to IR’s first argument, IR is correct that the amendment broadened the claim in certain respects—for instance, it eliminated the requirement that the "conductive electrode" at the bottom of the wafer be "coupled" to the drain conductive region, a requirement that the examiner described as "unsupported by neither [sic] the technology nor the specification." At the same time, however, IR chose to introduce the term "adjoining." This term excludes structures that might have been covered by the original claim language, because the "support body" of the old claim—apparently the "further region of opposite conductivity type" of the amended claim—was only required to "support[] said lightly doped major body portion," not necessarily to touch it. The amendment therefore narrowed the scope of the claim, at least with respect to the addition of the term "adjoining." Under such circumstances, IR cannot argue that the amendment was broadening merely because it eliminated some claim limitations.

As to IR’s second argument, we disagree with IR that the purpose of the amendment was tangential to the asserted equivalent. It is true that the reason given by the examiner for the rejection was that not all of the limitations in the original claim 43 were supported by the specification, and that IR overcame the rejection by amending the claim to contain only the structural limitations disclosed in the text of the specification and the drawing that became ’699 patent figure 8. In this regard, IR is correct that the claim is not necessarily limited to a particular mode of operation, but rather covers a particular structure that, in practice, may or may not function in unexpected ways. However, IR’s decision to claim that structure using the limiting term "adjoining," whether or not required to overcome the rejection, cannot be
described as only tangentially related to the equivalency of a structure with non-adjoining regions. With the amended language, IR recited precisely the structure it disclosed, and thereby overcame the examiner’s § 112 rejection. See Schwarz Pharma, Inc. v. Paddock Labs., Inc., 504 F.3d 1371, 1377 (Fed. Cir. 2007) ("The fact that the inventors may have thought after the fact that they could have relied on other distinctions in order to defend their claims is irrelevant and speculative . . . .").

Accordingly, we hold that prosecution history estoppel bars IR from asserting infringement of the "adjoining" limitation under the doctrine of equivalents, and we reverse the district court’s entry of judgment as to the "adjoining" claims.