Application of Carlson

• Decision Date: 03 July 1969
• Docket Number: Patent Appeal No. 8164.
• Parties: Application of David J. CARLSON.
• Court: U.S. Court of Customs and Patent Appeals (CCPA)

56 CCPA 1309, 412 F.2d 255 (1969)

Application of David J. CARLSON.

Patent Appeal No. 8164.

United States Court of Customs and Patent Appeals.

July 3, 1969.

Charles I. Brodsky, for appellant. A. Russinoff, Princeton, N.J., E.M. Whitacre, of counsel.

Joseph Schimmel, Washington, D. C., for the Commissioner of Patents, Jere W. Sears, Washington, D. C., of counsel.

Before RICH, Acting Chief Judge, HOLTZOFF and McLAUGHLIN, Judges, sitting by designation, ALMOND and BALDWIN, Judges.

BALDWIN, Judge.

This appeal is from the Patent Office Board of Appeals decision affirming the examiner's rejection of claims 4 and 23 in appellant's application¹ on the ground of double patenting for failing to patentably distinguish over the claims of the copending application of Hofstein,² assigned to the assignee of the instant application. Claims 6, 9-19, 22, and 24 have been allowed.

THE INVENTION

The invention relates to electrical circuitry involving an insulated gate, field-effect semiconductor. As background, a semiconductor of this general type usually includes a substrate of doped semiconductor material. Majority carriers may be caused to flow along a channel from a source contact to a drain contact on the substrate in response to an applied bias potential. A gate electrode adjacent to and insulated from the channel may have a varying potential applied thereto relative to the source to modulate the flow of majority carriers along the channel, thus providing an amplifying action.

In the particular construction of appellant's device, illustrated in Figure 2,

the substrate 12 of lightly doped silicon is provided with source and drain regions S and D containing diffused N type impurities. The interfaces between the source region and the substrate and between the drain region and the substrate may constitute internal rectifying junctions within the device.³ The gate electrode 22, overlying the channel C along which charge carriers flow from source to drain, is insulated from the channel by a layer of oxide 28. The gate electrode is offset toward the source and away from the drain. Of particular interest is a connection to the substrate, shown in Figure 2 as the metal plate 26 having a wire for making a circuit connection.

Circuit applications for the substrate connection are disclosed in three exemplary amplifying circuits shown in Figures 8, 9 and 10. In each of those circuits, the connection to the substrate cooperates with the internal rectifying junctions previously referred to, in order to achieve a particular circuit operation.⁴ However in the absence of disclosure of the internal rectifying junctions, such as for the first three circuits of the application shown in Figures 5, 6 and 7, the specification ascribes no circuit significance to the provision of a connection to the substrate.⁵

THE REJECTED CLAIMS

Claim 4 is directed to electrical circuitry including an insulated gate field-effect semiconductor, and we have emphasized the portion which appellant asserts patentably distinguishes over the Hofstein claims.

4. In combination:

an insulated gate field effect semiconductor device having a pair of electrodes connected to each other by a conductive channel and being located in spaced relation on a silicon substrate, and a gate electrode insulated from said silicon substrate and located so that the distance between said gate electrode and one of said pair of electrodes is longer than the distance between said gate electrode and the other one of said pair of electrodes, said conductive channel providing a path for current flow between said pair of electrodes in a direction corresponding to the relative polarity of the potential between said electrodes, circuit means for coupling said other one of said pair of electrodes to said substrate of semiconductor material,

an input circuit connected between said gate electrode and said other of said pair of electrodes, and

an output circuit including a d. c. voltage source connected between said pair of electrodes so that said one electrode is biased positively relative to said other electrode whereby said one electrode operates, as a drain electrode, said other electrode operates as a source electrode and the signal fed back through the inherent capacitance between said gate electrode and said drain electrode is reduced because of the displacement of said gate electrode toward the electrode which operates as a source electrode. Emphasis added.

Claim 23 is directed to electrical circuitry including an insulated gate, field-effect semiconductor, not restricted to the offset gate type, and reads:

23. In combination, a semiconductor device including a substrate of semiconductor material having spaced source and drain regions therein, said source and drain regions defining a current path of controllable conductivity, and a gate electrode insulated from said substrate and overlying at least a portion of said current path for controlling the conductivity thereof, and circuit means providing connections to said gate electrode, said source and drain regions and said substrate of semiconductor material. Emphasis added.

THE REFERENCE

Hofstein discloses that as an improvement on an insulated gate, field-effect semiconductor, the gate electrode may be offset toward the source and away from the drain to reduce the capacitance between the drain and gate electrodes thereby reducing the coupling between the input and output of the device. Other advantages of the offset gate are that the operating frequency of the device is increased and its transconductance is improved. The Hofstein device is provided with electrical circuit connections to the source, gate and drain electrodes only.

Although claim 4 of Hofstein's application was regarded as exemplary by the examiner for the double patenting rejection, the Hofstein patent issued without that claim. However, the board on reconsideration indicated that it considered the issues to be the same because of claim 2 of the Hofstein patent, which reads:

2. A field-effect transistor comprising a body of semiconductor material having a substantially planar surface, a thin layer of insulating material on said surface, a semiconductor channel in said body and extending entirely adjacent and substantially parallel to said surface, a source region adjacent said surface connected to one end of said channel, a drain region adjacent said surface connected to the other end of said channel, said source and said drain regions defining the ends of a charge carrier path through said channel substantially parallel to said surface, and a single continuous gate electrode structure comprising at least one metallic electrode on said insulating layer and opposite a continuous portion of said charge carrier path, one end of said gate electrode structure being closer physically to said source region than the other end of said gate electrode structure is to said drain region.

THE REJECTION

In rejecting the claims on appeal as failing to patentably distinguish from the claims of the commonly assigned Hofstein patent, the examiner set forth his position as to claim 4 as follows:

The remaining difference between the appealed claim 4 and claim 4 of the copending application * * * is the "circuit means for coupling said other one of said pair of electrodes to said substrate of semiconductor material." * * * This recitation does not patentably distinguish from the connection of the other one of said electrodes to said substrate that is inherent to the electrode being located on the substrate. The phrase "circuit means" calls for no distinctive means in that the structure set forth could be broadly construed as the connection of the electrode to the substrate by whatever manner it is connected, whether it be diffused to the substrate, or formed to the substrate in any manner. "Circuit means", without more, does not patentably distinguish from the connection of the electrode to the substrate.

As to claim 23, the examiner explained the rejection thus:

The sole feature structurally distinguishing claim 23 from claim 4 of Serial No. 245,086, is a recitation of "circuit means providing connections to said gate electrode, said source and drain regions and said substrate of semiconductor material." It is believed to be abundantly clear that a semiconductor device, to be rendered useful in a circuit, must obviously have means for connecting the device in the circuit. For this reason, the sole differentiating recitation, set forth above, is deemed to be one which does not patentably distinguish the compared claims in that the mere addition of operating connections is an immaterial limitation.

The board affirmed the rejection "for the reasons set forth in the Examiner's Answer" and adhered to that position on reconsideration.

OPINION

No terminal disclaimer has been filed in this case and, as indicated earlier, the claims are rejected for failure to patentably distinguish⁶ over claim 2 of the commonly assigned Hofstein patent.

Considering claim 23 first, the examiner's position was...