concurring in the judgment of invalidity of the ’313 patent and dissenting from the judgment of invalidity of the ’609 patent.
I join the majority’s holding that the ’389 patent was not infringed. I conclude, however, that the ’313 patent is invalid because of the on-sale bar under 35 U.S.C. 102(b) (1994), and that the ’609 patent is invalid for double patenting.
I.
With regard to the ’313 patent, the claims of the patent, in my view, are not enabled by the 1969 parent application for the ’712 patent and are, therefore, not entitled to priority based on the filing date of that application. As a result, the priority date of the ’313 patent is its filing date. Because it is undisputed that a sale of the claimed invention occurred more than one year prior to the filing date of the ’313 patent, that patent must be held invalid under 35 U.S.C. § 102(b).
Under 35 U.S.C. § 120 a claim in a continuation-in-part application that is directed solely to subject matter adequately disclosed under 35 U.S.C. § 112, first paragraph, in the parent application is entitled to claim priority from the filing date of the parent application. Transco Prods. Inc. v. Performance Contracting, Inc., 38 F.3d 551, 557 n. 6, 32 USPQ2d 1077, 1082 n. 6 (Fed.Cir.1994). If the claim, however, recites a feature which was first introduced in the continuation-in-part application and was not adequately disclosed in the parent application, that claim in the continuation-in-part application is not entitled to the filing date of the parent application. Id., at 557 n. 6, 32 USPQ2d at 1082 n. 6.
One of the requirements of § 112, first paragraph, for an adequate disclosure is that the invention must be described in “such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains” to make and use the invention.1 § 112, ¶ 1; Kennecott Corp. v. Kyocera Int’l, Inc., 835 F.2d 1419, 1421, 5 USPQ2d 1194, 1196-97 (Fed.Cir.1987). The issue of whether a disclosure is enabling is a matter of law. Lindemann Maschinenfabrik GMBH v. American Hoist and Derrick Co., 730 F.2d 1452, 1463, 221 USPQ 481, 489 (Fed.Cir.1984).
In this case, the district court determined that the ’313 patent is entitled to the filing date of the 1969 application for the ’712 patent. The court recognized that the ’313 patent claimed a particular way to reduce crystallographic slip, specifically using “same side” lamp heating. In this process, the heating lamps are placed on the same side of the susceptor as the substrate to heat the substrate directly. The court noted that Figure 6 of the 1969 application shows “same side” lamp heating. Based solely on that figure, the court concluded that the 1969 application inherently enabled the ’313 patent. The court made this determination even though the trial testimony was equivocal on whether operation of Figure 6 would produce a product free of crystallographic slip and despite its conclusion that using the reactor shown in Figure 6 in accordance with the 1969 application would not guarantee freedom from slip from all causes. Significantly, even one of the inventors could not testify that the operation of Figure 6 would necessarily produce a slip-free product.
*1576The district court erred in its inherency analysis. “[I]t is not sufficient that a person following the disclosure might obtain the result set forth in the [claim]; it must invariably happen.” Gubelmann v. Gang, 56 C.C.P.A. 1013, 408 F.2d 758, 766, 161 USPQ 216, 222 (1969). In this case, nothing in the 1969 application or in the record before the court shows that a material without crystallographic slip would invariably result from operation of Figure 6.
The claims of the ’313 patent are specifically directed to a method for heating substrate members formed of a single crystal material with “substantially no crystallographic slip.” An extensive disclosure concerning crystallographic slip and how to avoid it was added to the application for the ’313 patent. For example, the new disclosure in the application for the ’313 patent describes how thermal gradients and less than perfect contact between the substrate and the susceptor cause slip and it describes how these problems may be avoided. These features are specifically recited in claim l.2 The ’712 patent, on the other hand, does not even mention slip or crystallographic slip. While the original application shows generally same-side heating in Figure 6, it does not show or teach how to produce material with substantially no crystallographic slip. This method of producing no crystallographic slip is first disclosed in the ’313 patent.
Because the claims of the ’313 patent are all directed to new matter introduced in the continuation-in-part application which is not described or disclosed in the 1969 application, I conclude they are not entitled to the benefit of the filing date of the 1969 application. Accordingly, the ’313 patent should be held invalid under 35 U.S.C. § 102(b).
II.
The double patenting issue concerns two competing interests: protecting a patentee from the consequences of the Patent & Trademark Office’s (PTO) restriction practice, Studiengesellschaft Kohle mbH v. Northern Petrochem. Co., 784 F.2d 351, 358, 228 USPQ 837, 842 (Fed.Cir.1986) (Newman, J., concurring); and protecting the public from an unjustified extension of the patent term and, thus, the patentee’s right to exclude. In re Kaplan, 789 F.2d 1574, 1579-80, 229 USPQ 678, 683 (Fed.Cir.1986).
A restriction requirement is made during the prosecution of a patent application at the discretion of the Commissioner to avoid granting a patent for more than one invention. See 35 U.S.C. § 121 (“If two or more independent and distinct inventions are claimed in one application, the Commissioner may require the application to be restricted to one of the inventions.”). The Commissioner has issued strict guidelines in the Manual of Patent Examining Procedure (MPEP) to the examining corps as to when a restriction is appropriate. See MPEP § 803.01 (6th Ed.1995) (“Since requirements for restriction under Title 35 U.S.C. 121 are discretionary with the Commissioner, it becomes very important that the practice under this section be carefully administered.”). The restriction requirement also preserves revenue to the PTO and ensures the integrity of the PTO’s classification system. See 3 Donald S. Chi-sum, Patents § 12.01 at 12-2 (1995) (“Restriction is imposed to prevent subversion of the statutory fee structure for the application for and issuance of patents and to preserve the integrity of the system of examination *1577and classification within the Patent and Trademark Office.”).
Whole a restriction is made to ensure there is only one invention per patent, double patenting is concerned with the opposite problem, ensuring there is only one patent granted per invention. The policy underlying a double patenting rejection is an important policy because it precludes the improper extension of the statutory term of patent protection for an invention. This policy is likewise applicable to the judicially created doctrine of obviousness-type double patenting. Gerber Garment Technology, Inc. v. Ledra Sys., 916 F.2d 68B, 686 16 USPQ2d 1436, 1439 (Fed.Cir.1990) (Obviousness-type double patenting involves claims in two applications or patents that “were drawn to inventions so very much alike as to render one obvious in view of the other and to effectively extend the life of the patent that would have the earlier of the two issue dates.”). For obviousness-type double patenting, this problem can sometimes be avoided for co-owned patents or applications through the use of a terminal disclaimer. In re Longi, 759 F.2d 887, 894, 225 USPQ 645, 649 (Fed.Cir.1985).
Section 121 of Title 35 affords some protection against arguments of double patenting for a patent issued on a divisional application that was filed as a result of a restriction requirement. Specifically, the third sentence of § 121 provides:
A patent issuing on an application with respect to which a requirement for restriction under this section has been made, or on application filed as a result of such a requirement, shall not be used as a reference either in the Patent and Trademark Office or in the courts against a divisional application or against the original application or any patent issued on either of them.
This court has ruled, however, that the protection of § 121 is only available for claims issued on a divisional application that are consonant with the examiner’s restriction requirement. Gerber, 916 F.2d at 688, 16 USPQ2d at 1440. In Gerber the court stated:
Consonance requires that the line of demarcation between the “independent and distinct inventions” that prompted the restriction requirement be maintained. Though the claims may be amended, they must not be so amended as to bring them back over the line imposed in the restriction requirement. Where that line is crossed the prohibition of the third sentence of Section 121 does not apply.
Id., at 688,16 USPQ2d at 1440.
In this case the claims as amended during prosecution of the divisional application crossed the examiner’s precise and unambiguous line of demarcation. Thus, these claims cannot claim the protection of 35 U.S.C. § 121. Because the claims have lost the immunity of § 121, the claims must be held invalid for obviousness-type double patenting. Without this protection, Applied concedes that the claims as issued are obvious over the apparatus claims of the parent application.
The trial court erred in determining that consonance was not lost because the patents remain separately classified. The grounds for restriction are not solely dependant on separate classification. Section 121 permits a restriction for “independent and distinct inventions,” which the PTO construes to mean that the sets of claims must be drawn to separately patentable inventions. See MPEP § 802.01 (stating that the term distinct means two or more disclosed subjects that while perhaps related, such as process and apparatus for its practice, “ARE PATENTABLE (novel and unobvious) OVER EACH OTHER (though they may each be unpatentable because of the prior art)”). The mere fact that there are separate apparatus and method claims in the same application is not grounds for a restriction. See Symbol Technologies, Inc. v. Opticon, Inc., 935 F.2d 1569, 1580, 19 USPQ2d 1241, 1249 (Fed.Cir.1991) (determining that method and apparatus claims are not necessarily directed to separate inventions). The PTO correctly recognizes these may be just two different ways of claiming the same invention.
Therefore, under the PTO guidelines for restricting claims covering an apparatus and method of using the apparatus, the examiner must show one way distinctiveness. See *1578MPEP § 806.05(e). That is, either the apparatus or method must be capable of being practiced without the other. Id. In addition, the examiner must give a reason why it would be a burden to examine both sets of claims; commonly, the reason will be that there are separate classifications requiring independent searches. Id. at § 803. If both criteria are met, then the examiner may issue a restriction requirement.
In this ease the examiner issued a restriction requirement between two sets of apparatus claims and a set of method claims. The examiner restricted the method claims from the apparatus claims on the grounds that they were limited to a gaseous epitaxial deposition process while the apparatus claims were not. Specifically, the examiner stated that the method claims were distinct from the apparatus claims because the apparatus “could be used for non-epitaxial deposition” and that, as a result, a restriction was necessary. Applied has not shown that it ever challenged the examiner’s restriction or that the examiner’s grouping of the claims was incorrect.
After the restriction, Applied filed the method claims in a divisional application that issued as the ’609 patent fourteen years after the issuance of the patent on the parent application. The method claims in the ’609 patent, however, were not limited to an epitaxial deposition process. During the pro-section of the divisional application, the claims were amended to eliminate the epitaxial limitation. Thus, the very reason the examiner could and did require a restriction was eliminated. And, as Applied admits, but for the immunity of section 121, the method claims, which expire in 2002, are no longer patentable over the apparatus claims, which expired in 1988.3
The majority opinion recognizes that loss of consonance may result in double patenting but concludes that in this case “consonance was not violated, for the process claims remained in separate patents from the apparatus claims although the scope of the process claims was modified.” This is not the proper test and begs the very question we are asked to answer. Under this analysis no patent could ever be invalid for double patenting based on another patent because the claims would be in separate patents. Certainly that cannot be true. Indeed, in Gerber, this court held a patent that had been subject to a restriction requirement invalid for obviousness-type double patenting on the basis of the separate parent patent. 916 F.2d at 689, 16 USPQ2d at 1441.
I do not suggest that after a restriction has been imposed claims may never be modified. Rather, as Gerber and the language of § 121 instruct, the issue is whether the inventions claimed remain independent and distinct. As discussed above, in this case the very reason the examiner said the inventions were distinct — that the method claims were drawn to epitaxial deposition — was eliminated. The modification of the claims to cover non-epitaxial deposition resulted in consonance being lost.
To support its conclusion that the examiner’s line of demarcation among the separate inventions was not violated, the majority relies on Texas Instruments Inc. v. United States Int’l Trade Comm’n, 988 F.2d 1165, 26 USPQ2d 1018 (Fed.Cir.1993). In that case, the examiner’s groupings of the restricted claims was inconsistent with his written description of the groupings. When the validity of the patent resulting from the subsequent divisional application was challenged, we held that the actual restriction groupings, and not the written description of the groupings, controlled for purposes of determining whether subsequent amendments resulted in claims consonant with the restriction requirement. Id. at 1179, 26 USPQ2d at 1029. Because the claims as amended were consonant with the “grouping restriction actually imposed by the examiner,” the claims were protected under § 121 from allegations of double patenting. Id., at 1179, 26 USPQ2d at 1029. That is not the situation presented by this case. Here, the examiner’s demarcation was clearly the epitaxial deposition method claims, and the examiner did not *1579include claims directed to any matter outside that group.
While the examiner should have detected the loss of consonance, see Gerber, 916 F.2d at 685,16 USPQ2d at 1438 (“Non-compliance with the consonance requirement is normally detected by the PTO examiner.”), the paten-tee is not shielded by § 121 merely because of the examiner’s failure. For the protections of § 121 to apply, Applied had to keep the claims within the scope of the restriction requirement. Gerber, 916 F.2d at 688, 16 USPQ2d at 1440 (explaining that in order to gain the benefits of § 121, the patent applicant “must have limited the claims in its divisional application to the non-elected invention or inventions”).
When Applied failed to maintain consonance with the restriction requirement by broadening its claims to cover non-epitaxial, as well as epitaxial, deposition methods, it sought to cover the same invention as claimed in its apparatus patent that expired in 1988. This double patenting improperly extends its patent right beyond the statutory term.
. Because I conclude that the claims of the '313 patent are not enabled by the 1969 application, I do not reach the question of whether the best mode requirement of § 112, first paragraph, is satisfied,
. Claim 1 is as follows:
1. A method for heating a plurality of substrate members formed of a single crystal material with substantially no crystallographic slip in a process for the formation of semiconductor regions by epitaxial growth, said method comprising the steps of:
placing the substrate members in intimate contact with a susceptor body on one side of the same in a cool wall reaction chamber,
heating the substrate members and the sus-ceptor body directly and simultaneously in an unfocused, substantially uniform field of radiant heat energy produced by a bank of high intensity radiant heat lamps located on the same side of the susceptor body as the substrate members,
whereby the substrate members are heated uniformly and without appreciable thermal gradients by a combination of direct radiation from the heat lamps and heat transfer from the susceptor body, and
introducing a gaseous reactant into the reaction chamber to effect deposition of a chemical vapor coating on the substrate members.
. The patentees admitted during the prosecution of the '609 patent that the process of the '609 patent is the method of using the apparatus covered by United States Patent Nos. 3,623,712 and 4,047,496.