JP5098268B2 - Carbon nanotube growth method, carbon nanotube structure, and field effect transistor - Google Patents

Description

  The present invention relates to a carbon nanotube growth method, a carbon nanotube structure formed thereby, and a field effect transistor using the structure. In particular, a carbon nanotube growth method characterized by a region close to the catalytic metal for carbon nanotube growth suitable for increasing the current and the current density in a field effect transistor having a carbon nanotube channel, and thereby forming the carbon nanotube And a field effect transistor using the structure.

  Field-effect (FET) transistors using carbon nanotubes as channels have been studied, and many reports have been seen. However, most of them are limited to DC operation confirmation, and there is no report of formation of a transistor capable of sufficient high-speed operation intended for application to a high-frequency circuit. This is because the diameter of the carbon nanotube that becomes the channel is as small as several nanometers, so the ratio of the surface area to the volume is large and it is easily affected by the surroundings, and the number of carbon nanotubes that become the channel is about several in the past. This is because the current that can be driven is as small as about 10 μA. That is, the conventional carbon nanotube field effect transistor has a problem that the parasitic capacitance ratio with respect to the intrinsic capacitance is very large and high speed operation cannot be performed as compared with, for example, a MOS transistor (for example, Non-Patent Document 1). .

 In order to increase the current drive capability per unit gate width of this transistor, the amount of driveable current is increased by increasing the number of carbon nanotubes serving as channels per unit gate width, and consequently the parasitic capacitance is reduced. It becomes possible. That is, increasing the number of carbon nanotubes per unit gate width is the key to realizing high-speed operation.

  In order to fabricate a field effect transistor using carbon nanotubes as a channel, first, between a set of catalytic metal patterns for growing carbon nanotubes formed with a predetermined spacing on an insulating layer, Carbon nanotubes need to be cross-linked.

  FIG. 7 shows a schematic cross-sectional view of a structural example in which carbon nanotubes are cross-linked and conventionally studied. In the example shown in FIG. 7A, an insulating layer 102 such as a silicon oxide film is formed on a substrate 101 such as a silicon substrate or a sapphire substrate, and a carbon nanotube growth catalyst such as iron is formed thereon. A set of catalytic functional metal regions 103 made of metal and having a predetermined interval is formed. Further, as shown in the figure, the electrode 104 for electric field application growth is formed of a set of two rows, for example, titanium or the like, outside the two rows of catalytic functional metal regions 103 (Non-patent Document 1).

  Here, as will be described in detail later, a bridging gas such as acetylene gas is allowed to flow in a high temperature state, and at the same time, a direct current voltage is applied between the electric field application growth electrodes 104, thereby cross-linking between the catalytic functional metal regions 103. A plurality of carbon nanotubes grow in a shape. More specifically, the growth from the surface of the one catalytic functional metal region 103 and its cross-section and the cross-linking of the surface of the other catalytic functional metal region 103 and its cross-sectional portion are performed.

  However, in the case of the configuration as in this example, the catalytic functional metal region 103 is usually thin (for example, 1 nm or less), and the catalytic functional metal region 103 where the carbon nanotubes start to grow in order to crosslink the carbon nanotubes. Since the surface of the insulating layer 102 on the substrate 101 is very close to the surface of the substrate 101, the distance between the two rows of catalytic functional metal regions 103 is constant (for example, about 1 μm, which will be described later) As shown in the figure, the grown carbon nanotube 105 comes into contact with the substrate due to the growth direction and interaction (Van der Waals force), and the growth stops, and the other medium-functional metal region 103 is shown. The cross-link formation is almost impossible. Of course, in this case, a large number of carbon nanotubes start growing from one medium-functional metal region 103 (in this case, the left side), and if the distance between the two rows of catalytic functional metal regions 103 is short, a certain number of carbon nanotubes One reaches the other metal-functional metal region 103 (in this case, the right side), and cross-linking can be established. However, in the case of this example, it can be said that the possibility that the crosslinking is established is very low.

Therefore, as shown in FIG. 7B, the height of the two rows of catalytic functional metal regions 103 from the substrate 101 is increased, and the contact with the substrate side as seen in the example of FIG. Considered to avoid. As shown in the drawing, specifically, a thick SiO2 film (for example, about 200 nm thickness) formed on the substrate 101 is used, and this is wet-etched by wet etching patterning to have a predetermined height in two rows. A step pattern 106 was formed. Similarly, a catalytic functional metal region 103 is formed on the top, which serves as a mask for the above wet etching. (Note that the subsequent process of forming the electrode 104 for electric field application growth is not described because it is not directly related to this study.)
The two rows of catalytic functional metal regions 103 thus formed are formed at a distance from the substrate 101, but the wet-etch insulating step pattern 106 has a tapered structure as shown in the figure. In this situation, when carbon nanotubes are grown in the same manner as described above, many carbon nanotubes interact with this tapered shape (van der Waals force) in the initial stage of cross-linking growth from the catalytic functional metal region 103 on the left side. Works and the growth proceeds along the taper. Then, it was found that many carbon nanotubes contact the substrate 101 as shown in the figure before cross-growth with the catalytic functional metal region 103 on the right side, and the growth stops. In such a configuration, the number of cross-linked carbon nanotubes is quite limited.

Therefore, the configuration shown in FIG. 7C was examined in order to use such an insulating step without a taper. After laminating a thick insulating film on the substrate 101 and then laminating a catalytic functional metal film thereon, a photoresist pattern is formed at a predetermined position by photolithography to form two rows of protrusion patterns for carbon nanotube cross-linking growth. Then, using this resist pattern as a mask, dry dry etching to etch the catalytic functional metal film and then the thick insulating film, and strip the resist mask by a dry process, and then dry etching insulating step pattern 107 and the top catalytic functional metal region 103 was obtained. (The subsequent process of forming the electrode 104 for electric field application growth is omitted.)
Thus, the dry etching insulating step pattern 107 without a taper was produced. However, due to the above-described dry etching process of each insulating film, the resist of the mask is damaged and deteriorated, and even if the altered resist is subjected to a peeling process, the residue cannot be removed sufficiently. As a result, it has been found that even when the carbon nanotube cross-linking growth process similar to the above is performed, the number of carbon nanotubes grown as expected from the catalytic functional metal region 103 cannot be observed. Of course. In this case, since the cross-linking situation greatly depends on the remaining residue, there still remains a problem in reproducibility for each manufactured sample.
J. Appenzeller et al .; IEEE Transaction on Nanotechnology, Vol.1, No.4, Dec. 2002, pp184-189

  As described above, between the two rows of catalytic functional metal regions, which is a key point in fabricating a field effect transistor having a carbon nanotube channel and capable of high-speed operation, that is, high current driving capability per unit gate width. In order to efficiently grow a large number of carbon nanotubes by cross-linking, first, interaction between the catalytic functional metal region and the underlying substrate or an insulating step formed so as to separate the catalytic functional metal region from the substrate occurs. It was found that there was no need to make such a configuration. At the same time, it is necessary to avoid a process that inhibits the cross-linking growth.

  Accordingly, an object of the present invention is to produce an electric field effect transistor having a carbon nanotube as a channel and capable of increasing current density and operating at high speed, and there is no interaction between the catalytic functional metal region and the configuration in the vicinity thereof. Another object of the present invention is to provide a carbon nanotube growth method, a structure, and a field effect transistor using the same, which can avoid a process that inhibits cross-linking growth.

The growth method for the above purpose is:
Sequentially stacking a first insulating layer, a second insulating layer having an etching rate lower than that of the first insulating layer, and a catalytic metal layer on the surface of the substrate;
Etching the catalyst metal layer, the second insulating layer, and the first insulating layer to form at least two rows of protrusion patterns;
And a method of growing carbon nanotubes by applying an electric field between the two rows of protrusion patterns.

In addition, the above target structure is
A substrate,
At least a first insulating layer on the substrate surface, a second insulating layer having an etching rate lower than that of the first insulating layer on the first insulating layer, and a catalytic metal on the second insulating layer And at least two rows of protrusion patterns having a shape in which the second insulating layer is overhanging on the first insulating layer , and
This is made possible by a carbon nanotube structure characterized by comprising a carbon nanotube formed in a bridge between the two rows of adjacent protrusion patterns.

And the field effect transistor of the said objective is
A substrate,
At least a first insulating layer on the substrate surface, a second insulating layer having an etching rate lower than that of the first insulating layer on the first insulating layer, and a catalytic metal on the second insulating layer And at least two rows of protrusion patterns having a shape in which the second insulating layer is overhanging on the first insulating layer , and
A channel portion made of carbon nanotubes formed in a cross-linked manner between the two rows of protrusion patterns adjacent to each other;
Above the substantially central portion of the carbon nanotubes and one which is formed on the source electrode and a drain electrode formed on the other of the ends of the carbon nanotube, and a gate electrode formed between the source electrode and the drain electrode It is made possible by a field effect transistor characterized by comprising:

  The method, structure, and FET of the present invention greatly increase the number of carbon nanotube bridges between the protrusion patterns. As a result, the FET using this structure as a channel has a current drive per unit gate width. Therefore, a field effect transistor capable of high-speed operation can be manufactured.

  In addition, since the method employed does not require the use of a special apparatus, there is an advantage that it can be easily applied to a manufacturing process.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Example)
1 to 6 are schematic cross-sectional views illustrating a process for producing a field effect transistor (CNT-FET) using a carbon nanotube as a channel according to the present invention.

  As shown in FIG. 1A, a SiN layer 2 is formed on a substrate 1 made of a sapphire plate. This SiN layer 2 was formed with a film thickness of about 200 nm under the conditions of a substrate temperature of about 250 ° C. and a pressure of about 1 Torr using a plasma CVD apparatus using monosilane, ammonia, and nitrogen as reaction gases.

  Next, the SiO2 layer 3 is laminated thereon. This SiO 2 layer 3 is formed with a film thickness of about 20 nm under the conditions of a substrate temperature of about 300 ° C. and a pressure of about 0.15 Torr using an LP (low pressure) -CVD apparatus using monosilane and oxygen as reaction gases. It was.

  Next, an Fe (iron) layer 4 which is a catalytic metal having a catalytic action for carbon nanotube growth was laminated thereon with a film thickness of 0.5 nm using a sputtering apparatus.

  Then, as shown in FIG. 1B, a set of two rows (A and B) of resist patterns 5 having a predetermined interval are formed on the laminated film by using a known photolithography method. . The interval between the resist patterns 5A and 5B is one design factor that determines the channel length of the CNT-FET, and is an interval at which a plurality of carbon nanotubes are crosslinked (for example, about 2 to 3 μm). In FIG. 1 (2), the cross section of each resist pattern 5 is shown in a mesa structure (a trapezoidal structure with a convex cross section), but it is not necessarily limited to this, and a vertical cross section structure ( The cross section may be a rectangular structure).

  Next, as shown in FIG. 1C, a set of two rows (A and B) of protrusion patterns is formed on the substrate 1 by wet etching using the A and B resist patterns 5 as a mask. In this example, by using a buffered hydrofluoric acid solution as an etchant for wet etching, the Fe layer 4 is first patterned by this to form an Fe pattern 6, and then the SiO 2 layer 3 is formed using the Fe pattern 6 as a mask. A patterned SiO2 pattern 7 is formed, and a SiN pattern 8 in which the SiN layer 2 is patterned is formed, so that protrusion patterns A and B are formed.

  At this time, the etching rate of the SiN film and the Si2 film with respect to the buffered hydrofluoric acid solution that is an etchant is about 10 times faster in the SiN film, so that the SiN pattern 8 is first in accordance with the progress of the etching process. The SiO2 pattern 7 which is thin and has a low etching rate can be formed to overhang the SiN pattern 8.

  In this example, since an Fe film was used as the catalyst metal, a buffered hydrofluoric acid aqueous solution was used as an etchant. This film was first etched, and then the SiO 2 film / so that the SiO 2 film overhangs the SiN film with the same etchant. Etching of the laminated film of the SiN film was performed. However, the catalytic metal is not limited to this, and for example, vanadium, manganese, cobalt, nickel, molybdenum, tantalum, and the like are also applicable. Therefore, it is always possible to etch these films with a buffered hydrofluoric acid aqueous solution and pattern them. Is not limited. In this case, the applied catalytic metal film is first patterned with another suitable etchant, and then the SiO2 film / SiN film is overlaid with a buffered hydrofluoric acid solution using this metal film as a mask so that the SiO2 film overhangs the SiN film. The stacked film may be etched.

  Further, as shown in the figure, the combination of films formed by wet etching so that the upper insulating film pattern overhangs the lower insulating film pattern is not limited to the combination of the above-described SiO2 film / SiN film. Needless to say, the etchant used for this is not limited to the buffered hydrofluoric acid aqueous solution described above, and an etchant suitable for the combination of each film and overhang etching may be applied.

  Further, in the same figure, the SiO2 pattern 7 is overhanging the SiN8 pattern and is shown in a mesa structure (a trapezoidal structure with a cross-section protruding upward). The mesa-like structure is not necessarily required, and a vertical cross-sectional structure (a structure having a rectangular cross section) may be used. However, although the figure in which the width of the upper surface of the SiO2 pattern 7 is formed to be substantially the same as the width of the Fe pattern 6 (so as to be even narrower) is shown, such a situation is more feasible. Since carbon nanotubes start to grow from the top and side of the film, it is preferable in terms of avoiding the interaction with the lower film as much as possible from the viewpoint of continuous growth of carbon nanotubes, but this is not necessarily the case. .

  Next, as shown in FIG. 2 (4), the resist pattern 5 on the protrusion patterns A and B is removed by a wet process using a known organic solvent.

  Then, on both outer sides of the two protrusion patterns A and B, a pair of electric field application required electrode patterns for growing carbon nanotubes while applying an electric field is formed by a resist lift-off method using benzene.

  For this purpose, first, as shown in FIG. 2 (5), using a benzene-treated resist, an electrode pattern for applying an electric field is formed on the substrate 1 having the projection patterns A and B using a contact exposure apparatus. Transfer and apply a known photolithography method to form a lift-off resist pattern 9 in order to form an electric field applying electrode pattern by lift-off as shown in the figure.

  Then, as shown in FIG. 2 (6), a Ta (tantalum) film 10 having a thickness of 10 nm is deposited on the substrate 1 having the lift-off resist pattern 9 by sputtering.

  Next, as shown in FIG. 3 (7), by removing the lift-off resist pattern 9 using an organic solvent, an unnecessary Ta film is removed at the same time, and a C and D set of Ta films is used for electric field application. The electrode 10 is formed.

  Next, as shown in FIG. 3 (8), the CVD method was used, acetylene gas was used as the process gas, Ar gas or hydrogen gas was used as the carrier gas, and the Fe pattern 6 of the catalytic metal was formed on the top. For example, at a growth temperature of 600 ° C. under a pressure of 100 Pa, a direct current electric field is applied to the electrode 10 for electric field application formed on both ends of the pair of protrusion patterns A and B. A plurality of carbon nanotubes 12 are grown so as to bridge between the Fe patterns 6 of the top catalyst metal.

  Next, source / drain electrodes are formed on both ends of the carbon nanotube 12. For this purpose, the resist is formed by a resist lift-off method using benzene in the same manner as described with reference to FIGS. As shown in FIG. 3 (9), using a benzene-treated resist, the pattern of the source / drain electrodes is transferred onto the substrate 1 on which the carbon nanotubes 12 are formed by using a contact exposure apparatus. A photolithography method is applied to form a lift-off resist pattern 13 in order to form source / drain electrodes by lift-off as shown in the figure.

  Then, as shown in FIG. 4 (10), Pd (palladium) with a thickness of 100 nm, Ti (titanium) with a thickness of 10 nm, Pt with a thickness of 200 nm are formed on the substrate 1 having the resist pattern 13 for lift-off using the EB vapor deposition method. A Pd / Ti / Pt film 14 made of (platinum) is deposited.

  Next, as shown in FIG. 4 (11), by removing the lift-off resist pattern 12 using an organic solvent, unnecessary Pd / Ti / Pt films are removed at the same time, and a pair of Pd / Ti of E and F is removed. A source / drain electrode 15 (the distance between the source / drain electrodes E and F is, for example, about 1 to 2 μm) made of a / Pt film is formed.

  Next, a gate electrode is formed above the carbon nanotube 12. For this purpose, first, as shown in FIG. 4 (12), a SiN film 16 used as a passivation film is deposited on the substrate 1 after the formation of the source / drain electrodes. (Of course, as shown in the figure, the SiN film 16 passes between the cross-linked carbon nanotubes 12 and is also deposited on the lower side of the carbon nanotubes 12.) The SiN film 16 contains monosilane, ammonia, and nitrogen. Using a plasma CVD method as a reactive gas, a film thickness of about 400 nm was formed under conditions of a substrate temperature of about 250 ° C. and a pressure of about 1 Torr.

  Then, as shown in FIG. 5 (13), the gate electrode pattern is transferred onto the resist by using a contact exposure apparatus on the passivation film SiN film 16, and after development processing, a resist pattern 17 having an opening 18 is formed. Form.

  Next, the SiN film 16 is etched from the opening 18 in the depth direction, and an oxide film (residual oxide film) at a portion corresponding to the gate oxide film between the carbon nanotube 12 serving as the channel portion and the gate electrode is sufficiently obtained. It is necessary to control the thickness (for example, about 50 nm). On the other hand, the width of the gate electrode in the direction of the source / drain electrode 15 must also be controlled to a value (for example, 1 μm or less) within the narrow interval between the electrodes E and F. That is, since the etching of the SiN film 16 from the opening 18 requires fine dimensional control, an etching method with excellent vertical controllability is essential. Therefore, we formed the gate electrode using the following method.

  As shown in FIG. 5 (14), first, the RIE apparatus is used from the opening 18 to dry-etch the SiN film 16 by about 300 nm under the condition of CF4 as a reaction gas and a pressure of 12 mTorr, and then with a buffered hydrofluoric acid solution An additional wet etching of about 50 nm is performed to control the remaining film thickness. As a result, as shown in the figure, an overhang shape is formed on the SiN 16 side of the opening 18 starting from the edge of the resist pattern 17 of the opening 18. Is formed.

  The spacer lift-off method is applied using this overhang shape. That is, as shown in FIG. 5 (15), a Ti / Au film 19 made of Ti (titanium) having a thickness of 10 nm and Au (gold) having a thickness of 100 nm is formed on the substrate 1 including the opening 18 by EB vapor deposition. Deposit.

  Then, as shown in FIG. 6 (16), the unnecessary Ti / Au film 19 is removed together with the resist using an organic solvent, and the gate electrode 20 (for example, about 0.5 to 1 μm in width) is formed at the bottom of the opening 18. Is formed.

  As described above, by using the carbon nanotube formation method and the carbon nanotube cross-linking structure of the present invention, a plurality of carbon nanotubes 12 that have undergone many cross-linkings are used as channels, and the source / drain electrodes 15 A field effect transistor (FET) composed of (E and F) and the gate electrode 20 was formed.

  In order to confirm the effectiveness of the present invention, an FET (sample No. TR) having a channel formed by a carbon nanotube produced by the method and structure of the present invention, that is, crosslinked by a protrusion pattern having an overhang according to the present invention. The measured drain current of −071, the source-drain distance of 1.5 μm, was 32 μA.

  On the other hand, a vertical cross-sectional protrusion pattern (protrusion pattern as illustrated in FIG. 7C) having no overhang is used, and other fabrication conditions are FETs (sample no. , TR-052, the source-drain distance 1.5 μm) was 13 μA.

  As described above, in this case, a current increase of about 2.5 times as a drain current is observed. According to the method of the present invention, the distance between the source and drain electrodes ( In other words, the number of carbon nanotubes cross-linked between the protrusion patterns was greatly increased, and the effectiveness of the method, structure, and FET of the present invention was confirmed.

  Further, the method of the present invention does not require an apparatus or process peculiar to this method, and has an advantage that it can be easily introduced into a manufacturing process. It was also found that if the same manufacturing conditions were used, the variation in the manufacturing conditions was not large.

  Note that the manufacturing conditions, manufacturing method, dimensions, and the like described in this embodiment are examples for explanation, and they can be changed without departing from the gist of the present invention.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Appendix 1)
Sequentially stacking a first insulating layer, a second insulating layer having an etching rate lower than that of the first insulating layer, and a catalytic metal layer on the surface of the substrate;
Etching the catalyst metal layer, the second insulating layer, and the first insulating layer to form at least two rows of protrusion patterns;
And a step of growing a carbon nanotube by applying an electric field between the two rows of protrusion patterns.

(Appendix 2)
2. The carbon nanotube growth method according to claim 1, wherein the first insulating layer is a silicon nitride film, and the second insulating layer is a silicon oxide film.

(Appendix 3)
The carbon nanotube growth method according to appendix 1 or 2, wherein the etchant for the etching is a buffered hydrofluoric acid aqueous solution.

(Appendix 4)
A substrate,
At least two rows of at least a first insulating layer, a second insulating layer on the first insulating layer, and a catalytic metal layer on the second insulating layer are stacked on the substrate surface. Projection pattern,
A carbon nanotube structure comprising: carbon nanotubes formed between the two rows of protrusion patterns adjacent to each other.

(Appendix 5)
The carbon nanotube structure according to claim 4, wherein the first insulating layer is a silicon nitride film, and the second insulating layer is a silicon oxide film.

(Appendix 6)
The carbon nanotube structure according to appendix 4 or 5, wherein the substrate is a sapphire substrate.

(Appendix 7)
A substrate,
At least two rows of at least a first insulating layer, a second insulating layer on the first insulating layer, and a catalytic metal layer on the second insulating layer are stacked on the substrate surface. Projection pattern,
A channel portion made of carbon nanotubes formed in a cross-linked manner between the two rows of protrusion patterns adjacent to each other;
A source electrode formed at one of both ends of the carbon nanotube and a drain electrode formed at the other, and a gate electrode formed above the substantially central portion of the carbon nanotube and between the source electrode and the drain electrode And a field effect transistor comprising:

(Appendix 8)
The field effect transistor according to appendix 7, wherein the first insulating layer is a silicon nitride film, and the second insulating layer is a silicon oxide film.

(Appendix 9)
The field effect transistor according to appendix 7 or 8, wherein the substrate is a sapphire substrate.

FIG. 1 illustrates a manufacturing process of a field effect transistor of the present invention (part 1). FIG. 2 illustrates a manufacturing process of a field effect transistor of the present invention (part 2). The figure explaining the manufacturing process of the field effect transistor of this invention (the 3) FIGS. 4A and 4B illustrate a manufacturing process of a field effect transistor of the present invention (part 4) FIG. 5 illustrates a manufacturing process of a field-effect transistor of the present invention (No. 5). FIG. 6 illustrates a manufacturing process of a field-effect transistor of the present invention (No. 6) The figure explaining the conventional carbon nanotube bridge construction

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Substrate 2 SiN layer 3 SiO2 layer 4 Fe layer 5, 17 Resist pattern 6 Fe pattern 7 SiO2 1 pattern 8 SiN pattern 9, 13 Resist pattern for lift-off 10 Ta film 11 Electrode for applying electric field 12, 105 Carbon nanotube 14 Pd / Ti / Pt film 15 Source / drain electrode 16 SiN film 18 Opening 19 Ti / Au film
20 Gate electrode 102 Insulating layer 103 Catalytic metal forming region 104 Electrode for electric field application growth 106 Wet etch insulating step pattern 107 Dry etch insulating step pattern

Claims (5)

Sequentially stacking a first insulating layer, a second insulating layer having an etching rate lower than that of the first insulating layer, and a catalytic metal layer on the surface of the substrate;
Etching the catalyst metal layer, the second insulating layer, and the first insulating layer to form at least two rows of protrusion patterns;
And a step of growing a carbon nanotube by applying an electric field between the two rows of protrusion patterns.   2. The carbon nanotube growth method according to claim 1, wherein the first insulating layer is a silicon nitride film, and the second insulating layer is a silicon oxide film.   3. The carbon nanotube growth method according to claim 1, wherein the etchant for etching is a buffered hydrofluoric acid aqueous solution. A substrate,
At least a first insulating layer on the substrate surface, a second insulating layer having an etching rate lower than that of the first insulating layer on the first insulating layer, and a catalytic metal on the second insulating layer And at least two rows of protrusion patterns having a shape in which the second insulating layer is overhanging on the first insulating layer , and
A carbon nanotube structure comprising: carbon nanotubes formed in a bridge between the two rows of protrusion patterns adjacent to each other. A substrate,
At least a first insulating layer on the substrate surface, a second insulating layer having an etching rate lower than that of the first insulating layer on the first insulating layer, and a catalytic metal on the second insulating layer And at least two rows of protrusion patterns having a shape in which the second insulating layer is overhanging on the first insulating layer , and
A channel portion made of carbon nanotubes formed in a cross-linked manner between the two rows of protrusion patterns adjacent to each other;
Above the substantially central portion of the carbon nanotubes and one which is formed on the source electrode and a drain electrode formed on the other of the ends of the carbon nanotube, and a gate electrode formed between the source electrode and the drain electrode And a field effect transistor comprising:

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