Patent Publication Number: US-7217974-B2

Title: Output prediction logic circuits with ultra-thin vertical transistors and methods of formation

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation of U.S. application Ser. No. 10/164,611, filed on Jun. 10, 2002 now U.S. Pat. No. 6,900,521(Notice of Allowance dated Dec. 20, 2004), the disclosure of which is herewith incorporated by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates generally to the field of integrated circuits, and more specifically, to novel output prediction logic circuits and methods of formation. 
   BACKGROUND OF THE INVENTION 
   Complementary Metal Oxide Semiconductor (CMOS) technology is well-known in the fabrication of integrated circuits. CMOS technology is employed not only for analog integrated circuits, but also for digital integrated circuits to which they confer low power dissipation, high density of integration and low cost of fabrication. 
     FIG. 1  illustrates a prior art conventional static CMOS NAND gate circuit  10 . One of the drawbacks associated with the static CMOS NAND gate circuit  10  of  FIG. 1  is that each input  12 ,  14  must drive two gates, the gate of an NMOS transistor and the gate of a PMOS transistor. Input  12  drives gates  16  and  18 , while input  14  drives gates  20  and  22 . As a result, large CMOS circuitry area and large number of metal wiring levels must be utilized to allow interconnections. Another drawback is that the hole mobility in a PMOS transistor is about three times lower than the electron mobility in an NMOS transistor of comparable size. Accordingly, switching transients are very asymmetrical. To compensate the asymmetry of the switching transients, the PMOS transistors are often fabricated with a large width or size to provide symmetrical switching. Nevertheless, the increase in the size of the PMOS transistors increases the stray capacitive loads, which in turn requires an even larger area for the circuits and a very inefficient area utilization. 
   Output prediction logic (OPL) is a technique that applies to a variety of inverting logic families to increase speed considerably. OPL relies on the alternating nature of logical output values for inverting gates on a critical path. In other words, for any critical path, the logical values of the gates along that particular path will be alternating ones (1) and zeros (0). Since all gates are inverting, the OPL predictions will be correct exactly one-half the time. By correctly predicting exactly one half of the gate output, OPL obtains considerable speedups, of at least two times, over the underlying logic families, which can be, for example, static CMOS, pseudo-NMOS or dynamic logic. 
   Recently, in McMurchie L.; Kio, S.; Yee, G.; Thorp, T.; Sechen, C., Output prediction logic: a High-Performance CMOS Design Technique, Proc. International Conference on Computer Design, 2000, pp. 247–254, 2000 (the disclosure of which is incorporated herein), McMurchie et al. have described a very fast logic circuit that comprises integrated CMOS technology. One of the features of the integrated logic circuit family described by McMurchie et al. is that all of the outputs are precharged high. Only if necessary and if determined by the logic function, high performance NMOS transistors are then used to discharge the output node low. 
   Subsets of integrated fast logic circuit families, such as pseudo-NMOS, have been analyzed and described as being particularly suited to array-type applications. For example, in  Grounded load complementary FET circuits; SCEPTRE analysis , IEEE J. Solid-State Circuits, Vol. SC-8, No. 4, pp. 282–284 (1973), Sakamoto and Forbes have described a pseudo-NMOS implementation of CMOS circuits. In OPL, the lower performance PMOS devices in CMOS technology are used only for precharge functions which did not have critical speed requirements. Improvements of the pseudo-NMOS circuits analyzed by Sakamoto et al. are obtained as a result of a unique clocking scheme described here in employing OPL. 
   Although advances in the integration of CMOS logic families are becoming increasingly notable, a major disadvantage remains the slow speed of the integrated CMOS logic circuits. The conventional integrated CMOS logic circuit is considerably slower than the OPL circuit mainly because of the PMOS devices that charge an output node high if the logic input is appropriate. Thus, the use of PMOS devices for logical switching transitions generally results in a slower speed for the integrated CMOS logic circuit. 
   In addition to the drawbacks posed by the integration of CMOS logic families described above, the continuous scaling of MOSFET technology to reduce channel lengths to sub-micron dimensions causes significant problems in the conventional transistor structures. Because junctions depths should be much less than the channel length, junction depths should be of a few hundred Angstroms for channel lengths of 1000 Angstroms. Such shallow junctions are difficult to form by conventional implantation and diffusion techniques. Extremely high levels of channel doping are required to suppress short-channel effects such as drain induced barrier lowering, threshold voltage roll off, and sub-threshold conduction. Sub-threshold conduction is particularly problematic in dynamic circuits technology because it reduces the charge storage retention time on capacitor nodes. These extremely high doping levels result in increased leakage and reduced carrier mobility. Therefore, the improved performance achieved by making the channel shorter is negated by low carrier mobility. 
   Accordingly, there is a need in the art for a logic circuit with CMOS gate arrays with very high performance NMOS transistors and faster switching speeds. There is also a need for CMOS gate arrays with transistors where the surface space charge region scales down as other transistor dimensions scale down. A method for fabricating very high performance transistors and a gate array including such high performance transistors is also needed. A method for fabricating a very fast CMOS logic circuit, as well as a method of increasing the noise margin while maintaining the performance gain of such integrated CMOS logic circuits, are also needed. 
   BRIEF SUMMARY OF THE INVENTION 
   In one embodiment, the present invention provides very fast integrated CMOS logic circuits comprising CMOS gate arrays having ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body regions and strained silicon channels. The ultra-thin vertical NMOS transistors comprise a relaxed silicon germanium (SiGe) body region with a graded germanium content and a strained silicon channel in contact with the relaxed silicon germanium (SiGe) body region. 
   According to another embodiment of the present invention, ultra-thin body vertical NMOS transistors are fabricated by epitaxially growing a relaxed silicon germanium (SiGe) body region by ultra-high vacuum chemical vapor deposition (UHVCVD) and subsequently forming a strained silicon channel in contact with the relaxed silicon germanium (SiGe) body region. 
   According to yet another embodiment of the invention, CMOS gate arrays with ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body regions and strained silicon channels are employed to form a pseudo-NMOS OPL circuit. The pseudo-NMOS logic circuit includes a number of logic inputs, a clock input and an output. The number of logic inputs are coupled to a number of gates of the vertical ultra-thin NMOS transistors having relaxed silicon germanium (SiGe) body regions and strained silicon channels. The clock input is coupled to a gate of a vertical ultra-thin NMOS transistor with a relaxed silicon germanium (SiGe) body region and a strained silicon channel for precharging the output. The output is charged high by a PMOS device with a gate at ground potential. 
   In another embodiment of the invention, CMOS gate arrays comprising ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body regions and strained silicon channels are employed to form a dynamic OPL circuit. The dynamic logic circuit includes a number of logic inputs, a clock input and an output. The number of logic inputs are coupled to a number of gates of vertical ultra-thin NMOS transistors with relaxed silicon germanium (SiGe) body regions and strained silicon channels. The clock input is coupled to a gate of a vertical ultra-thin NMOS transistor with a relaxed silicon germanium (SiGe) body region and a strained silicon channel for precharging the output. The output is charged high by a PMOS transistor. 
   These and other embodiments, features and advantages of the present invention will become more fully apparent from the following detailed description of the exemplary embodiments of the invention which are provided in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram illustrating a conventional static CMOS logic circuit. 
       FIG. 2  illustrates a cross-sectional view of a semiconductor substrate on which ultra-thin vertical transistors with a strained silicon channel are fabricated according to an embodiment of the present invention. 
       FIG. 3  illustrates the semiconductor substrate of  FIG. 2  at a stage of processing subsequent to that shown in  FIG. 2 . 
       FIG. 4  illustrates the semiconductor substrate of  FIG. 2  at a stage of processing subsequent to that shown in  FIG. 3 . 
       FIG. 5  illustrates a partial three-dimensional of the semiconductor substrate of  FIG. 2  at a stage of processing subsequent to that shown in  FIG. 4 . 
       FIG. 6  illustrates a cross-sectional view of the the semiconductor substrate of  FIG. 4  taken along line  5 – 5 ′. 
       FIG. 7  illustrates the semiconductor substrate of  FIG. 6  at a stage of processing subsequent to that shown in  FIG. 6 . 
       FIG. 8  illustrates the semiconductor substrate of  FIG. 6  at a stage of processing subsequent to that shown in  FIG. 7 . 
       FIG. 9  illustrates the semiconductor substrate of  FIG. 6  at a stage of processing subsequent to that shown in  FIG. 8 . 
       FIG. 10  illustrates the semiconductor substrate of  FIG. 6  at a stage of processing subsequent to that shown in  FIG. 9 . 
       FIG. 11  is a top view illustrating wiring contacts consistent with ultra-thin vertical transistors with strained silicon channels as used in a 3-input NOR gate of a dynamic logic circuit fabricated according to the present invention. 
       FIG. 12  illustrates a schematic diagram for a pseudo NMOS OPL logic circuit fabricated according to the present invention. 
       FIG. 13  illustrates a schematic diagram for a dynamic OPL logic circuit fabricated according to the present invention. 
       FIG. 14  illustrates a processing system having ultra-thin vertical transistors with strained silicon channels formed according to embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following detailed description, reference is made to various specific embodiments in which the invention may be practiced. These embodiments are described with sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be employed, and that structural, logical, and electrical changes may be made. 
   The term “substrate” used in the following description may include any semiconductor-based structure that has a silicon surface. Structure must be understood to include silicon, silicon-on insulator (SOI), silicon-on sapphire (SOS), doped and undoped semiconductors, epitaxial layers of silicon supported by a base semiconductor foundation, and other semiconductor structures. The semiconductor also need not be silicon-based. The semiconductor could be silicon-germanium, germanium, or gallium arsenide. When reference is made to a substrate in the following description, previous process steps may have been utilized to form regions or junctions in or on the base semiconductor or foundation. 
   The present invention provides a method for the fabrication of integrated CMOS output prediction logic (OPL) circuits with very fast speed and decreased noise sensitivity. The very fast output prediction logic (OPL) circuits comprise CMOS gate arrays with ultra-thin vertical NMOS transistors having relaxed silicon germanium (SiGe) body regions and strained silicon channels. Each of the ultra-thin vertical NMOS transistors comprises a relaxed silicon germanium (SiGe) body region having a graded germanium (Ge) content and a strained silicon channel in contact with the relaxed silicon germanium (SiGe) body region. The CMOS gate arrays with the ultra-thin vertical NMOS transistors having relaxed silicon germanium (SiGe) body regions and strained silicon channels of the present invention may be employed in the fabrication of output prediction logic (OPL) circuits, for example, pseudo-NMOS OPL circuits and dynamic OPL circuits. 
   Referring now to the drawings, where like elements are designated by like reference numerals,  FIGS. 2–10  illustrate the fabrication of ultra-thin vertical NMOS transistors  300   a ,  300   b  ( FIG. 10 ) with relaxed silicon germanium (SiGe) body regions having a graded germanium content and with strained silicon channels. The fabrication of the ultra-thin vertical NMOS transistors  300   a ,  300   b  of  FIG. 10  requires steps which are similar in part with those employed in the fabrication of vertical PMOS and NMOS transistors, described before in the literature and which will not be described in detail below. For example, U.S. Pat. No. 6,072,209 to Noble et al. and U.S. Pat. No. 6,150,687 to Noble et al., the disclosures of which are incorporated by reference herein, have detail descriptions for the fabrication of vertical gates for vertical PMOS and NMOS transistors and outline steps which are similar in part to those of the present application, to the extent that the cited references refer to vertical PMOS and NMOS transistors having body regions formed of silicon and not to NMOS transistors having body regions of silicon germanium with a graded germanium content. For a better understanding of the present invention, however, the processing steps for the fabrication of the ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body region and strained silicon channels will be briefly described below. 
     FIG. 2  illustrates a semiconductor substrate  100  and a first source/drain layer  102  formed over the semiconductor substrate  100 . In the embodiments of the present invention described below, the semiconductor substrate  100  may be any of the following three different types of substrates:
         (i) lightly doped p-type;   (ii) silicon on insulator substrates, such as SIMOX, for example; and   (iii) islands of silicon on insulator formed by techniques such as those described in U.S. Pat. No. 5,691,230 to Forbes, the disclosure of which is incorporated by reference herein.       
   As known in the art, SIMOX (Separation by IMplanted OXygen) involves implanting a high dose of oxygen ions at a sufficiently deep level within a silicon substrate. A subsequent anneal step forms a buried oxide layer into the substrate. After the anneal step, an additional layer of epitaxial silicon is usually deposited to obtain a sufficiently thick silicon layer on which to form the desired device. 
   As also known in the art, a substrate of islands of silicon on insulator can be formed, for example, by directionally etching a silicon substrate to form a plurality of trenches between protruding silicon rows; forming a nitride cap on the silicon rows, extending partway down the sides of the trenches; isotropically etching the trenches to partially undercut the silicon rows; and oxidizing the substrate to fully undercut the silicon rows. 
   For simplicity and for a better understanding of the present invention, reference to the semiconductor substrate  100  will be made in this application as to p-type silicon substrate  100 . Similarly, although the first source/drain layer  102  ( FIG. 2 ) may be either an n+ silicon source/drain layer  102  (for NMOS transistors) or a p+ silicon source/drain layer  102  (for PMOS transistors), for the purposes of the present invention, the first source/drain layer  102  of  FIG. 2  would be considered an n+silicon source/drain layer  102 . The n+ silicon source/drain layer  102  may be formed by ion implantation, epitaxial growth, or a combination of these techniques. Vertical NMOS transistors with strained silicon channels and relaxed silicon germanium (SiGe) body regions will be formed on the n+ silicon source/drain layer  102  in accordance with embodiments of the present invention and as illustrated in more detail below. 
   Reference is now made to  FIG. 3 . A relaxed silicon germanium (SiGe) layer  105  with a graded germanium content is next formed over the first source/drain layer  102  to a thickness of about 2,000 Angstroms to about 40,000 Angstroms. According to an embodiment of the present invention, the relaxed silicon germanium (SiGe) layer  105  is epitaxially grown by an ultra high vacuum chemical vapor deposition (UHVCVD) method and using a linear graded buffer layer technique, as described by K Rim et al. in  Strained Si NMOSFETs for High Performance CMOS Technology , Symp. on VLSI Tech. Digest of Technical Papers, p. 59 (2001) and by K. Rim, et al. in  Fabrication and Analysis of Deep Submicron Strained - Si N - MOSFET&#39;s, IEEE Trans. Electron. Devices,  47, p. 1406 (2000), the disclosures of which are incorporated by reference herein. 
   As analyzed by Rim et al., the germanium (Ge) content in the silicon germanium (SiGe) layer  105  is graded in steps using a linear graded buffer layer technique, by increasing the germanium content from 0 to about 20% over a thickness of about 1.5 μm. The fully relaxed silicon germanium (SiGe) layer  105  with the graded germanium content is capped with a 7,000 Angstroms thick relaxed silicon germanium (SiGe) layer with a constant germanium content of about 20%. Dichlorosilane and germane are used as the silicon and germanium source precursors at growth temperatures of about 700° C. to about 750° C. As described in Rim et al., both the thickness of the relaxed silicon germanium (SiGe) layer  105  and the germanium (Ge) content in the silicon germanium (SiGe) layer are verified by cross-sectional TEM, Rutherford back-scattering and Raman spectroscopy. X-ray diffraction analysis quantified the germanium (Ge) content to about 15% and 20%. As explained in more detail below, the relaxed silicon germanium (SiGe) layer  105  with graded germanium (Ge) content acts as a buffer layer for strained silicon (Si) layer  120  ( FIG. 7 ), which will form a strained silicon channel for a vertical NMOS transistor fabricated according to the present invention. 
   Referring now to  FIG. 4 , a second source/drain layer  106  is formed over the relaxed silicon germanium (SiGe) layer  105  with graded germanium content. The second source/drain layer  106  may be formed by ion implantation, epitaxial growth, or a combination of these techniques. 
   A photoresist is subsequently applied and selectively exposed to provide a mask for the directional etching of trenches  109  ( FIGS. 5 ,  6 ) by reactive ion etching (RIE), for example. As shown in  FIG. 5 , the directional etching results in the formation of a plurality of pillars or column bars  150  ( FIG. 5 ) each comprising a stack of the first source/drain layer  102 , the relaxed silicon germanium (SiGe) layer  105  with graded germanium content and the second source/drain layer  106 . The resulting pillars or column bars  150  provide first and second source/drain regions  102  and  106 , respectively, and silicon germanium (SiGe) body region  105  for NMOS transistors  300   a ,  300   b  ( FIG. 10 ). Oxide layer  104  ( FIG. 6 ) is formed on the surface of the p+ silicon substrate  100  and the first source/drain layer  102  to surround the NMOS transistors  300   a ,  300   b  ( FIG. 10 ) with relaxed silicon germanium (SiGe) body regions  105  having graded germanium content. As noted above, the previously-mentioned processing steps for the fabrication of ultra-thin vertical pillars or column bars  150  are similar in part to the ones described in U.S. Pat. No. 6,072,209 to Noble et al. and U.S. Pat. No. 6,150,687 to Noble et al. (both of which are incorporated by reference herein) to the extent that the processing steps for vertical gate formation are similar, but the materials for the formation of the respective vertical transistors are different. 
   Referring now to  FIGS. 7–8 , a strained silicon layer of about 200 Angstroms to about 2,000 Angstroms is formed on each side of the relaxed silicon germanium (SiGe) body region  105  with graded germanium content and directionally etched to leave strained silicon channel layer  120  ( FIG. 7 ) on two opposing sidewalls of the pillars. As described by K. Rim et al. in  Strained Si NMOSFETs for High Performance CMOS Technology , Symp. on VLSI Tech. Digest of Technical Papers, p. 59 (2001), the strained silicon channel layer  120  may be epitaxially grown by an ultra high vacuum chemical vapor deposition (UHVCVD) method at about 1000° C. As reported by Rim et al., the strain state of the strained silicon channel layer  120  can be verified and confirmed by cross-sectional TEM, Rutherford back-scattering and Raman spectroscopy. 
   As analyzed by Rim et al., when strained silicon is formed on a relaxed germanium layer, a large lattice mismatch occurs between the relaxed germanium layer and the strained silicon layer. As also shown by M. Fischetti et al. in  Band structure, deformation potentials, and carrier mobility in strained Si, Ge, and SiGe alloys , J. of Appl. Phys., 80, p. 2234 (1996) (the disclosure of which is incorporated by reference herein), a pseudo-morphic layer of silicon formed on relaxed silicon germanium is under biaxial tensile strain which, in turn, modifies the band structure and enhances the carrier transport. In an electron inversion layer, the subband splitting is larger in strained silicon (Si) than in unstrained silicon because of the strain-induced band splitting in addition to that provided by quantum confinement. The ground level splitting (E 0 (d 4 )−E 0 (d 2 )) in an MOS inversion layer at 1 MV/cm transverse field is about 120 and about 250 meV for unstrained and strained silicon, respectively. 
   As demonstrated by J. Wesller et al. in  Strain Dependence of the Performance Enhancement in Strained - Si n - MOSFETs , IEDM Tech. Dig., p 373 (1994) and further by Mizuno et al. in  Advanced SOI - MOSFETs with Strained - Si Channel for High Speed CMOS - Electron/Hole Mobility Enhancement , Symp. on VLSI Tech., p. 210 (2000) (the disclosures of which are incorporated by reference herein), the increase in energy splitting reduces intervalley scattering and enhances NMOSFET mobility for vertical fields lower than about 0.6 MV/cm. Similarly, in  Transconductance Enhancement in Deep Submicron Strained - Si n - MOSFETs , IEDM Tech. Dig., p. 707 (1998) (the disclosure of which is incorporated by reference herein), K. Rim et al. have demonstrated that the increase in energy splitting reduces intervalley scattering and enhances NMOSFET mobility for vertical fields higher than about 1 MV/cm. According to the studies conducted by Rim et al., biaxial tensile strain in thin silicon layers grown pseudomorphically on relaxed silicon germanium layers splits the 6-fold degeneracy in a silicon conduction band. The splitting causes the 2-fold degenerate (Δ 2 ) valleys to be preferentially populated, suppressing intervalley scattering. 
   Finally, as shown by K. Rim, et al. in  Fabrication and Analysis of Deep Submicron Strained - Si N - MOSFET&#39;s, IEEE Trans. Electron. Devices,  47, p. 1406 (2000) (the disclosures of which is incorporated by reference herein), the scaled transconductance g m  is also improved due to the reduced density of states and enhanced non-equilibrium transport. As shown by Rim et al. in the above-mentioned study, although the strained and un-strained-Si MOSFETs exhibit similar short-channel effects, the intrinsic transconductance of the strained Si devices is enhanced by about 60% for the entire channel length range investigated. Rim et al. also concluded that reduced carrier-phonon scattering for electrons with average energies (less than a few hundred meV) accounts for the enhanced high-field electron transport in strained silicon layers. 
   Referring back to the drawings and as illustrated in  FIG. 8 , a thick oxide layer  130  of about 1,000 Angstroms to about 20,000 Angstroms is next formed over the strained silicon layer  120 . Another masking step can be employed to isotropically etch the oxide layer  130  off of some of the sidewalls of pillars or column bars  150  and leave the oxide only on one sidewall of each column bar  150  as required for particular configurations. Again, the above-described steps are similar in part to the ones detailed in U.S. Pat. No. 6,150,687 to Noble et al. and incorporated by reference in this application. 
   In  FIG. 9 , a gate oxide layer  140  is formed on the exposed sidewalls of the strained silicon layer  120 . The gate oxide  140  may be formed, for example, by thermal growth, or by dry oxidation at high temperatures under an oxygen atmosphere, or by thermally growing an oxynitride using a nitrogen and oxygen source. The drain and source regions of the NMOS transistors  300   a ,  300   b  are in the strained silicon channel layer  120  along the sidewalls of each pillar  105 . Although the embodiments illustrated above have been described with reference to the formation of vertical gate structures, the invention is not limited to this embodiment. Accordingly, the present invention contemplates the formation of ultra-thin body transistors with strained silicon channels which include other types of gate structures, such as for example, horizontal gate structures as described in U.S. Pat. No. 6,150,687 to Noble et al., or horizontal replacement gate structures, a variation of U.S. Pat. No. 6,150,687 to Noble et al described in U.S. patent application Ser. No. 09/596,266 filed Jun. 16, 2000. 
     FIG. 10  illustrates the formation of transistor gates  170  and wiring contacts  180 ,  182 . As shown in  FIG. 10 , the transistor gates  170 , which may be formed of polysilicon for example, are vertically oriented gates and are associated with a side of the pillars  150 . The transistor gates  170  of  FIG. 10  may be formed, for example, by a deposition method such as chemical vapor deposition (CVD) at a temperature of about 550° C. to about 650° C. and a pressure of less than about 2 Torr. The top portions of the CVD deposited polysilicon material located above the second source/drain layer  105  ( FIG. 10 ) are then removed by CMP, for example, to form the transistor gates  170 . If desired, dopants such as phosphorous, boron or nitrogen may be implanted subsequently into the transistor gates  170  to increase their conductivity.  FIG. 10  also illustrates the thick oxide layer  130  formed, as described above, on an opposing side of each of the pillar  150  for isolating the transistor gate  170  from neighboring pillars. 
   The ultra-thin vertical NMOS transistors  300   a ,  300   b  with relaxed silicon germanium (SiGe) body regions  105  and strained silicon channels  120  may be employed in the fabrication of vertical gate array structures comprising a plurality of such ultra-thin vertical NMOS transistors with strained silicon channels, with or without PMOS transistors. The ultra-thin vertical NMOS transistors  300   a ,  300   b  with strained silicon channel  120  may be also employed in the fabrication of gate array structures comprising other conventional planar structures, as described in the literature and formed by known conventional techniques, in addition to the vertical gate structures of the present invention. 
     FIG. 11  illustrates a logic gate implementation using ultra-thin vertical NMOS transistors having relaxed silicon germanium (SiGe) body regions with graded germanium content and strained silicon channels fabricated according to embodiments of the present invention. The logic gate implementation of  FIG. 11  is a dynamic 3-input NOR gate shown as circuit  500  of  FIG. 13 . As illustrated in  FIG. 11 , a number of logic inputs A, B, C are coupled to gates  351  for a number of ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body regions and strained silicon channels formed according to the present invention and illustrated as block  350 .  FIG. 11  further illustrates a clock input coupled to gate  331  of a PMOS transistor  330 . As one of ordinary skill in the art would realize, the circuit shown in  FIG. 11  comprises the PMOS transistor  330  coupled between a power supply (e.g. Vdd) and an output which precharges the output high during a precharge stage and prior to the arrival of a number of input signals as the number of logic inputs A, B and C. An output  380  is illustrated as coupled to both the PMOS transistor  330  and the number of ultra-thin vertical NMOS transistors with relaxed silicon germanium (SiGe) body regions with graded germanium content and strained silicon channels shown as the block  350 . The output  380  will be coupled to one of the number of inputs of a subsequent static logic circuit portion (not shown) as part of a CMOS logic circuit. 
     FIG. 12  illustrates the implementation of the ultra-thin vertical NMOS transistors  300   a ,  300   b  with silicon germanium (SiGe) body regions and strained silicon channels in the fabrication of a pseudo-NMOS output prediction logic (OPL) circuit  400 . In the pseudo-NMOS OPL circuit  400  of  FIG. 12 , all of the outputs are charged high by a PMOS device with a gate at ground potential. As analyzed by Kio, S.; McMurchie L.; Sechen, C. in  Application of Output Prediction Logic to Differential CMOS , Proc. IEEE Computer Society Workshop on VLSI, pp. 57–65, May 2001 and by McMurchie L.; Kio, S.; Yee, G.; Thorp, T.; Sechen, C.,  Output prediction logic: a High - Performance CMOS Design Technique , Proc. International Conference on Computer Design, 2000, pp. 247–254, 2000 (the disclosures of which are incorporated herein), the “enable” or “evaluate” NMOS gates of a pseudo-NMOS OPL circuit are then clocked in succession and the logical output of each gate determined. If the logic gate pulls the output low, a DC path to ground forms and the gate works on a static or DC basis. If the logical output is a high level, then the PMOS device just keeps the output high. 
   The pseudo-NMOS OPL circuit  400  of  FIG. 12  has an enable NMOS transistor at the bottom of the gate. When the clock (clk) is low, the gate is disabled, with the output being charged to a logic “1.” When the clock goes high, the gate is enabled and becomes a pseudo-NMOS gate. The pull-up PMOS serves both to precharge the gate and to correct a high output when it glitches. 
     FIG. 13  illustrates a dynamic output prediction logic (OPL) circuit  500  in which the PMOS transistor is clocked to precharge the output high. As also analyzed by Kio, S.; McMurchie L.; Sechen, C. in  Application of Output Prediction Logic to Differential CMOS , Proc. IEEE Computer Society Workshop on VLSI, pp. 57–65, May 2001 and by McMurchie L.; Kio, S.; Yee, G.; Thorp, T.; Sechen, C.,  Output prediction logic: a High - Performance CMOS Design Technique , Proc. International Conference on Computer Design, 2000, pp. 247–254, 2000 (the disclosures of which are incorporated herein), since the enable or evaluation function is performed at every gate in succession, the node will either be left high, or will be discharged to ground potential. These gates work only on a dynamic basis, by charge storage on capacitive nodes. As known in the art and as illustrated in  FIG. 13 , the OPL-dynamic gate looks similar to a domino gate, but with the output inverter missing. The gate precharges high, and the keeper transistor, if sized sufficiently large, will enable the output node to recover from glitches. As demonstrated by Kio, S.; McMurchie L.; Sechen, C. in  Application of Output Prediction Logic to Differential CMOS , Proc. IEEE Computer Society Workshop on VLSI, pp. 57–65, May 2001 (the disclosure of which is incorporated herein), if the clock arrives too early, a gate may glitch so much that the keeper transistor shuts off, causing the output voltage to remain at a value possibly well below Vdd or even zero. 
   Although the combination of the ultra-thin vertical NMOS transistors with silicon germanium body regions and strained silicon channels with the fastest OPL circuit families results in the fastest possible circuit operation, the ultra-thin vertical NMOS transistors  300   a ,  300   b  ( FIG. 10 ) of the present invention may be also incorporated in other semiconductor device, including various processor system components, such as for example, a central processing unit (CPU), or in any of the various types of memory devices, such as for example, RAM, ROM, and others. They may also be used in any type of integrated circuit controller for a floppy disk, a hard disk, a ZIP, or a CD-ROM disk. 
     FIG. 14  illustrates an exemplary processing system  900  which may utilize the ultra-thin vertical NMOS transistors  300   a ,  300   b  of the present invention. The processing system  900  includes one or more processors  901  coupled to a local bus  904 . A memory controller  902  and a primary bus bridge  903  are also coupled the local bus  904 . The processing system  900  may include multiple memory controllers  902  and/or multiple primary bus bridges  903 . The memory controller  902  and the primary bus bridge  903  may be integrated as a single device  906 . 
   The memory controller  902  is also coupled to one or more memory buses  907 . Each memory bus accepts memory components  908  which include at least one memory device  100  comprising at least one ultra-thin vertical NMOS transistor, such as the ultra-thin vertical NMOS transistors  300   a ,  300   b  of the present invention. The memory components  908  may be a memory card or a memory module. Examples of memory modules include single inline memory modules (SIMMs) and dual inline memory modules (DIMMs). The memory components  908  may include one or more additional devices  909 . For example, in a SIMM or DIMM, the additional device  909  might be a configuration memory, such as a serial presence detect (SPD) memory. The memory controller  902  may also be coupled to a cache memory  905 . The cache memory  905  may be the only cache memory in the processing system. Alternatively, other devices, for example, processors  901  may also include cache memories, which may form a cache hierarchy with cache memory  905 . If the processing system  900  include peripherals or controllers which are bus masters or which support direct memory access (DMA), the memory controller  902  may implement a cache coherency protocol. If the memory controller  902  is coupled to a plurality of memory buses  907 , each memory bus  907  may be operated in parallel, or different address ranges may be mapped to different memory buses  907 . 
   The primary bus bridge  903  is coupled to at least one peripheral bus  910 . Various devices, such as peripherals or additional bus bridges may be coupled to the peripheral bus  910 . These devices may include a storage controller  911 , an miscellaneous I/O device  914 , a secondary bus bridge  915 , a multimedia processor  918 , and an legacy device interface  920 . The primary bus bridge  903  may also coupled to one or more special purpose high speed ports  922 . In a personal computer, for example, the special purpose port might be the Accelerated Graphics Port (AGP), used to couple a high performance video card to the processing system  900 . 
   The storage controller  911  couples one or more storage devices  913 , via a storage bus  912 , to the peripheral bus  910 . For example, the storage controller  911  may be a SCSI controller and storage devices  913  may be SCSI discs. The I/O device  914  may be any sort of peripheral. For example, the I/O device  914  may be an local area network interface, such as an Ethernet card. The secondary bus bridge may be used to interface additional devices via another bus to the processing system. For example, the secondary bus bridge may be an universal serial port (USB) controller used to couple USB devices  917  via to the processing system  900 . The multimedia processor  918  may be a sound card, a video capture card, or any other type of media interface, which may also be coupled to one additional devices such as speakers  919 . The legacy device interface  920  is used to couple legacy devices, for example, older styled keyboards and mice, to the processing system  900 . 
   The processing system  900  illustrated in  FIG. 14  is only an exemplary processing system with which the invention may be used. While  FIG. 14  illustrates a processing architecture especially suitable for a general purpose computer, such as a personal computer or a workstation, it should be recognized that well known modifications can be made to configure the processing system  900  to become more suitable for use in a variety of applications. For example, many electronic devices which require processing may be implemented using a simpler architecture which relies on a CPU  901  coupled to memory components  908  and/or memory devices  100  comprising at least one ultra-thin vertical NMOS transistors  300   a ,  300   b . These electronic devices may include, but are not limited to audio/video processors and recorders, gaming consoles, digital television sets, wired or wireless telephones, navigation devices (including system based on the global positioning system (GPS) and/or inertial navigation), and digital cameras and/or recorders. The modifications may include, for example, elimination of unnecessary components, addition of specialized devices or circuits, and/or integration of a plurality of devices. 
   Accordingly, the above description and accompanying drawings are only illustrative of exemplary embodiments that can achieve the features and advantages of the present invention. It is not intended that the invention be limited to the embodiments shown and described in detail herein. The invention is limited only by the scope of the following claims.