# Patent

## Title
Semiconductor surrounding gate transistor device and production method therefor

## Abstract

The method includes the steps of: forming a planar semiconductor layer on an oxide film formed on a substrate and then forming a pillar-shaped first-conductive-type semiconductor layer on the planar semiconductor layer; forming a second-conductive-type semiconductor layer in a portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer; forming a gate dielectric film and a gate electrode made of a metal, around the pillar-shaped first-conductive-type semiconductor layer; forming a sidewall-shaped dielectric film on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode; forming a sidewall-shaped dielectric film on a sidewall of the gate electrode; forming a second-conductive-type semiconductor layer in an upper portion of the pillar-shaped first-conductive-type semiconductor layer.

## Background
RELATED APPLICATIONS
Pursuant to 35 U.S.C. §119(e), this application claims the benefit of the filing date of Provisional U.S. Patent Application Ser. No. 61/207,718 filed on Feb. 13, 2009. This application is a continuation application of PCT/JP2009/052558 filed on Feb. 16, 2009 which claims priority under 35 U.S.C. §365(a) to PCT/JP2008/052566 filed on Feb. 15, 2008. The entire contents of these applications are hereby incorporated by reference.


TECHNICAL FIELD
The present invention relates to a semiconductor device and a production method therefor.
BACKGROUND ART
A degree of integration in a semiconductor integrated circuit, particularly in an integrated circuit using a MOS transistor, has been increasing year by year. Along with the increase in the degree of integration, miniaturization of the MOS transistor used therein has progressed to a nano region. The progress in miniaturization of the MOS transistor gives rise to a problem, such as difficulty in suppressing a leak current, which poses an impediment to sufficiently reducing a circuit occupancy area while meeting a requirement of ensuring a necessary amount of current. With a view to solving this problem, there has been proposed a surrounding gate transistor (SGT) having a structure in which a source, a gate and a drain are arranged in a direction perpendicular to a substrate, wherein the gate is formed to surround a pillar-shaped semiconductor layer (see, for example, the following Patent Documents 1 to 3).
In the SGT, a channel region is provided around a side surface of the pillar-shaped semiconductor, so that a large gate width is achieved within a small occupancy area. This means that it is necessary to allow a large ON-current to flow through the small occupancy area. However, if the source, drain and gate have a high resistance, it becomes difficult to apply a desired voltage for allowing the flow of a large ON-current, to the source, drain and gate. Therefore, it is required to provide an SGT production method including a design technique for reducing the resistance of the source, drain and gate. As another condition for allowing the flow of a large ON-current, it is also required to reduce a resistance of a contact.
In a conventional MOS transistor, a gate is formed by depositing a gate material, transferring a gate pattern to a resist on a substrate by lithography, and etching the gate material. In other words, in the conventional MOS transistor, a gate length is designed based on a gate pattern.
In the SGT, a current flows in a direction perpendicular to the substrate, because the side surface of the pillar-shaped semiconductor serves as a channel region. Thus, in the SGT, a gate length is not designed based on a gate pattern but based on a production method, so that the gate length and a variation therein are determined by a production method.
In the SGT, as measures for suppressing an increase in leak current occurring along with miniaturization, it is required to reduce a diameter of the pillar-shaped semiconductor. It is also required to provide a production method capable of optimizing the source and drain to suppress short-channel effects so as to reduce a leak current.
As with the conventional MOS transistor, the SGT also has a need for reducing a production cost. For this purpose, it is required to reduce the number of production steps.
Instead of polysilicon, a metal can be used as a material for a gate electrode to suppress depletion and reduce a resistance of the gate electrode. In this case, any production step subsequent to the step of forming a metal gate has to be designed while taking into account metal contamination due to the metal gate.
Patent Document 1: JP 2-71556A
Patent Document 2: JP 2-188966A
Patent Document 3: JP 3-145761A
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an SGT production method which comprises a production step designed using a metal as a material for a gate electrode while taking into account metal contamination, and allows a structure for reducing a resistance of a source, drain and gate, a desired gate length, desired source and drain configurations and a desired diameter of a pillar-shaped semiconductor to be obtained.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a method of producing a semiconductor device, which comprises the steps of (a) forming a planar semiconductor layer on an oxide film formed on a substrate and then forming a pillar-shaped first-conductive-type semiconductor layer on the planar semiconductor layer, (b) forming a second-conductive-type semiconductor layer in a portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, (c) forming a gate dielectric film and a gate electrode made of a metal, around the pillar-shaped first-conductive-type semiconductor layer, (d) forming a sidewall-shaped dielectric film on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode, (e) forming a sidewall-shaped dielectric film on a sidewall of the gate electrode, (f) forming a second-conductive-type semiconductor layer in an upper portion of the pillar-shaped first-conductive-type semiconductor layer, (g) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, (h) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer, (i) forming a contact on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, and (j) forming a contact on the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer.
Preferably, in the method of the present invention, a distance between a central axis of the pillar-shaped first-conductive-type semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped first-conductive-type semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film formed on the sidewall of the gate electrode.
Preferably, in the method of the present invention, the planar semiconductor layer, the first-conductive-type semiconductor layer, and each of the second-conductive-type semiconductor layers, are a planar silicon layer, a first-conductive-type silicon layer, and a second-conductive-type silicon layer, respectively.
Alternatively, in the method of the present invention, the planar semiconductor layer, the first-conductive-type semiconductor layer, and each of the second-conductive-type semiconductor layers, may be a planar silicon layer, a p-type silicon layer or a non-doped silicon layer, and an n-type silicon layer, respectively.
Alternatively, in the method of the present invention, the planar semiconductor layer, the first-conductive-type semiconductor layer, and each of the second-conductive-type semiconductor layers, may be a planar silicon layer, an n-type silicon layer or a non-doped silicon layer, and a p-type silicon layer, respectively.
Preferably, in the method of the present invention, the step (a) includes the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; implanting an impurity into the initial silicon layer through the pad oxide film to adjust a threshold, and then subjecting the initial silicon layer to annealing to activate and diffuse the impurity so as to promote uniform distribution of the impurity in the initial silicon layer; and forming a silicon nitride film for use as a mask during formation of the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, the step (a) includes the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer; forming a silicon oxide film on the silicon nitride film; applying a resist onto the silicon oxide film, forming a pattern having an inverted shape of a top view of the pillar-shaped first-conductive-type silicon layer, using the resist by lithography, and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer; forming an amorphous silicon or polysilicon film to fill the hole formed in the silicon oxide film; polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing; removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask; sacrificially oxidizing the amorphous silicon or polysilicon film-based mask to reduce a size of the amorphous silicon or polysilicon film-based mask; and etching the amorphous silicon or polysilicon film-based mask to remove the sacrificial silicon oxide film on a surface thereof.
Alternatively, in the method of the present invention, the step (a) may include the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer; forming a silicon oxide film on the silicon nitride film; applying a resist onto the silicon oxide film, forming a pattern having an inverted shape of a top view of the pillar-shaped first-conductive-type silicon layer, using the resist by lithography, and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer; depositing an oxide film and etching back the oxide film to reduce a diameter of the hole penetrating through the silicon oxide film; forming an amorphous silicon or polysilicon film to fill the hole formed in the silicon oxide film; polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing; and removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask.
Preferably, in the method of the present invention, the step (a) includes the sub-steps of: dry-etching a silicon nitride film and a pad oxide film deposited on an initial silicon layer, using an amorphous silicon or polysilicon film-based mask serving as the second hard mask, to form a silicon nitride film-based mask serving as the first hard mask; forming the pillar-shaped first-conductive-type silicon layer by dry etching using the first hard mask and the second hard mask; and, when the amorphous silicon or polysilicon film-based mask serving as the second hard mask is fully etched away to cause a change in plasma emission intensity detectable by a dry etching apparatus, performing a dry-etching end-point detection process by detecting the change in the plasma emission intensity, to control a height dimension of the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, a thickness of the amorphous silicon or polysilicon film-based mask serving as the second hard mask is less than a height dimension of the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, the step (b) includes the sub-steps of: sacrificially oxidizing the pillar-shaped first-conductive-type silicon layer fabricated on the planar silicon layer to form a sacrificial oxide film as a means for reducing irregularities in a region of the sidewall of the pillar-shaped first-conductive-type silicon layer serving as a channel region, removing a silicon surface implanted with a foreign substance typified by carbon during the dry etching, and protecting the pillar-shaped first-conductive-type silicon layer from contaminations typified by-products to be produced during dry etching in a subsequent step; applying a resist onto the planar silicon layer, and forming a pattern for the second-conductive-type silicon layer to be formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, using the resist by lithography; and dry-etching the planar silicon layer to form the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then removing the resist.
Preferably, in the method of the present invention, the step (b) includes introducing a second-conductive-type impurity into a surface of the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer on which there is a silicon nitride film-based mask by an impurity doping process typified by impurity implantation, using the sacrificial oxide film formed during the sacrificial oxidation of the pillar-shaped first-conductive-type silicon layer, as a screen oxide film, to form the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, a diameter of the pillar-shaped first-conductive-type silicon layer is less than that of the silicon nitride film-based mask serving as the first hard mask.
Preferably, in the method of the present invention, an implantation angle during the impurity implantation for use in forming the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer is in the range of 0 to 6 degrees.
Preferably, in the method of the present invention, the second-conductive-type silicon layer is formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, without implanting the impurity into the upper portion of the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, the step (c) includes the sub-step of: oxidizing a silicon surface of the pillar-shaped first-conductive-type silicon layer with silicon nitride film-based mask fabricated on the planar silicon layer, and etching the silicon nitride film-based mask to reduce a diameter of the silicon nitride film-based mask to be less than that of the pillar-shaped first-conductive-type silicon layer, so as to allow a part of a high-k gate dielectric film to be removed based on dry etching in a subsequent step.
Preferably, in the method of the present invention, the step (c) includes the sub-steps of: removing the sacrificial oxide film by etching from a pillar-shaped first-conductive-type semiconductor layer with a silicon nitride film-based mask and a sacrificial oxide film formed on the planar semiconductor layer and a planar semiconductor layer having a second-conductive-type semiconductor layer formed therein, forming gate dielectric film of a high-k film such as a hafnium oxide film, and forming a metal film as a gate electrode material, to allow the pillar-shaped first-conductive-type silicon layer to be buried therein; and polishing the metal film by chemical mechanical polishing to flatten an upper surface of the gate electrode material, wherein the silicon nitride film-based mask serving as the first hard mask is used as a stopper for the chemical mechanical polishing to control an amount of chemical mechanical polishing with high repeatability.
Preferably, in the method of the present invention, the step (c) includes the sub-steps of: etching back the flattened metal film serving as the gate electrode material to allow the resulting metal film to have a desired gate length of the gate electrode; and forming a silicon oxide film on respective upper surfaces of the pillar-shaped first-conductive-type semiconductor layer and the etched-back metal film serving as the gate electrode material, wherein the silicon oxide film covers the metal film to allow subsequent steps to be performed without taking into account metal contamination, and protects the upper surface of the gate electrode material from a wet or dry treatment to be performed in a subsequent step, so as to suppress a change in the gate length and damage of the gate dielectric film from the side of the upper surface thereof.
Preferably, in the method of the present invention, the step (c) includes the sub-steps of: forming a silicon nitride film on the silicon oxide film to have a film thickness derived by subtracting a film thickness of the silicon oxide film from a sum of a desired film thickness of the gate electrode and a film thickness of the gate dielectric film; etching back the silicon nitride film and the silicon oxide film to form a silicon nitride film-based sidewall and a silicon oxide film-based sidewall, wherein a sum of a film thickness of the silicon nitride film-based sidewall and a film thickness of the silicon oxide film-based sidewall which determine a sum of a film thickness of the gate electrode to be formed by the metal film and the film thickness of the gate dielectric film is controlled by adjusting a film thickness of the silicon nitride film to be formed in the sub-step of forming a silicon nitride film, and conditions for the etching-back in the sub-step of etching back the silicon nitride film, so as to allow the gate electrode to have the desired film thickness; applying a bottom antireflective coating (BARC) layer and a resist, and forming a pattern for a gate line, using the resist by lithography; and etching the BARC layer, the silicon oxide film, and the metal film serving as the gate electrode material, using the resist as a mask to form the gate electrode and the gate line. Further, the steps (d) and (e) include the sub-steps of: removing the silicon nitride film-based mask, the silicon nitride film-based sidewall and the silicon oxide film-based sidewall on an upper portion of the pillar-shaped first-conductive-type silicon layer by dry etching or wet etching; and forming a silicon oxide film and a silicon nitride film and etching back the silicon nitride film and the silicon oxide film to expose an upper surface of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and a top surface of the pillar-shaped first-conductive-type silicon layer, while forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film, on the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer and in contact with the top of the gate electrode, and forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film on the sidewall of the gate electrode. The step (f) includes introducing a second-conductive-type impurity into an upper portion of the pillar-shaped first-conductive-type silicon layer through an impurity doping process typified by impurity implantation, to form the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, and the steps (g) and (h) include subjecting each of the upper surface of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and an upper surface of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, to sputtering of a metal such as nickel (Ni) or cobalt (Co), and a heat treatment, and removing an unreacted metal film, to form the metal-semiconductor compound on each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer. In this case, the silicon oxide film-based sidewalls and the silicon nitride film-based sidewalls serve as a means to isolate the gate electrode from each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, so as to prevent short-circuiting between the gate electrode and each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, due to the metal-semiconductor compounds, and the silicon nitride film-based sidewall covering the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer serves as a means to control formation of a metal-semiconductor compound from the side of the sidewall of the pillar-shaped first-conductive-type silicon layer.
Preferably, in the method of the present invention, the steps (i) and (j) include the sub-steps of: forming a film typified by a silicon nitride film to serve as a contact stopper; forming a silicon oxide film to serve as an interlayer film and then flattening the silicon oxide film by chemical mechanical polishing; forming contact holes on respective ones of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, a gate line extending from the gate electrode, and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, by etching.
Preferably, in the method of the present invention, the sub-step of forming contact holes includes etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, and then etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.
Alternatively, in the method of the present invention, the sub-step of forming contact holes may include etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.
Alternatively, in the method of the present invention, the sub-step of forming contact holes may include etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.
Alternatively, in the method of the present invention, the sub-step of forming contact holes may include etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.
According to a second aspect of the present invention, there is provided a semiconductor device which comprises: a planar semiconductor layer formed on a substrate, wherein the planar semiconductor layer has a second-conductive-type semiconductor layer formed therein and a metal-semiconductor compound formed on the second-conductive-type semiconductor layer; a pillar-shaped first-conductive-type semiconductor layer formed on the planar semiconductor layer, wherein the pillar-shaped first-conductive-type semiconductor layer has a second-conductive-type semiconductor layer formed in an upper portion thereof and a metal-semiconductor compound formed on the second-conductive-type semiconductor layer; a gate dielectric film formed around the pillar-shaped first-conductive-type semiconductor layer; a gate electrode made of a metal and formed to surround the gate dielectric film; a sidewall-shaped dielectric film formed on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode; and a sidewall-shaped dielectric film formed on a sidewall of the gate electrode.
Preferably, in the semiconductor device of the present invention, a distance between a central axis of the pillar-shaped first-conductive-type semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped first-conductive-type semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film formed on the sidewall of the gate electrode.
The semiconductor device production method of the present invention comprises the steps of (a) forming a planar semiconductor layer on an oxide film formed on a substrate and then forming a pillar-shaped first-conductive-type semiconductor layer on the planar semiconductor layer, (b) forming a second-conductive-type semiconductor layer in a portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, (c) forming a gate dielectric film and a gate electrode made of a metal, around the pillar-shaped first-conductive-type semiconductor layer, (d) forming a sidewall-shaped dielectric film on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode, (e) forming a sidewall-shaped dielectric film on a sidewall of the gate electrode, (f) forming a second-conductive-type semiconductor layer in an upper portion of the pillar-shaped first-conductive-type semiconductor layer, (g) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, (h) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer, (i) forming a contact on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, and (j) forming a contact on the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer. This makes it possible to provide an SGT production method which comprises a production step designed using a metal as a material for a gate electrode while taking into account metal contamination, and allows a structure for reducing a resistance of a source, drain and gate, a desired gate length, desired source and drain configurations and a desired diameter of a pillar-shaped semiconductor to be obtained.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A-1D are tables showing steps of a semiconductor production method according to one embodiment of the present invention.
FIG. 2(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 2(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 2(a).
FIG. 3(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 3(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 3(a).
FIG. 4(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 4(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 4(a).
FIG. 5(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 5(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 5(a).
FIG. 6(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 6(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 6(a).
FIG. 7(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 7(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 7(a).
FIG. 8(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 8(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 8(a).
FIG. 9(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 9(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 9(a).
FIG. 10(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 10(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 10(a).
FIG. 11(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 11(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 11(a).
FIG. 12(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 12(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 12(a).
FIG. 13(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 13(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 13(a).
FIG. 14(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 14(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 14(a).
FIG. 15(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 15(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 15(a).
FIG. 16(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 16(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 16(a).
FIG. 17(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 17(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 17(a).
FIG. 18(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 18(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 18(a).
FIG. 19(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 19(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 19(a).
FIG. 20(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 20(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 20(a).
FIG. 21(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 21(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 21(a).
FIG. 22(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 22(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 22(a).
FIG. 23(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 23(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 23(a).
FIG. 24(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 24(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 24(a).
FIG. 25(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 25(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 25(a).
FIG. 26(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 26(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 26(a).
FIG. 27(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 27(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 27(a).
FIG. 28(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 28(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 28(a).
FIG. 29(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 29(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 29(a).
FIG. 30(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 30(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-N in FIG. 30(a).
FIG. 31(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 31(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 31(a).
FIG. 32(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 32(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 32(a).
FIG. 33(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 33(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 33(a).
FIG. 34(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 34(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 34(a).
FIG. 35(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 35(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 35(a).
FIG. 36(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 36(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 36(a).
FIG. 37(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 37(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 37(a).
FIG. 38 is an explanatory sectional view showing a product in FIGS. 37(a) and 37(b).
FIG. 39(a) is a top plan view showing a step in one modification of the semiconductor production method according to the embodiment.
FIG. 39(b) is a sectional view showing the step in the modification of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 39(a).
FIG. 40(a) is a top plan view showing a step in the modification of the semiconductor production method according to the embodiment.
FIG. 40(b) is a sectional view showing a step in the modification of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 40(a).
FIG. 41(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 41(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 41(a).
FIG. 42(a) is a top plan view showing one of the steps of the semiconductor production method according to the embodiment
FIG. 42(b) is a sectional view showing the step of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 42(a).
FIG. 43(a) is a top plan view showing a step of one modification of the semiconductor production method according to the embodiment
FIG. 43(b) is a sectional view showing the step of the modification of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 43(a).
FIG. 44(a) is a top plan view showing a step of the modification of the semiconductor production method according to the embodiment
FIG. 44(b) is a sectional view showing the step of the modification of the semiconductor production method according to the embodiment, taken along the line A-A′ in FIG. 44(a).



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred embodiment of the present invention, a distance between a central axis of the pillar-shaped first-conductive-type semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped first-conductive-type semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film formed on the sidewall of the gate electrode. This makes it possible to form a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, so that a resistance of the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer can be reduced.
In a preferred embodiment of the present invention, the step (a) includes the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; implanting an impurity into the initial silicon layer through the pad oxide film to adjust a threshold, and then subjecting the initial silicon layer to annealing to activate and diffuse the impurity so as to promote uniform distribution of the impurity in the initial silicon layer; and forming a silicon nitride film for use as a mask during formation of the pillar-shaped first-conductive-type silicon layer. In this case, the pad oxide film for reducing a stress between a silicon layer and a silicon nitride film to be formed in the next step can be used as a screen oxide film during impurity injection. This makes it possible to reduce the number of production steps so as to reduce a production cost.
In a preferred embodiment of the present invention, the step (a) includes the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer; forming a silicon oxide film on the silicon nitride film; applying a resist onto the silicon oxide film, forming a pattern having an inverted shape of a top view of the pillar-shaped first-conductive-type silicon layer, using the resist by lithography, and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer; forming an amorphous silicon or polysilicon film to fill the hole formed in the silicon oxide film; polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing; removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask; sacrificially oxidizing the amorphous silicon or polysilicon film-based mask to reduce a size of the amorphous silicon or polysilicon film-based mask; and etching the amorphous silicon or polysilicon film-based mask to remove the sacrificial silicon oxide film on a surface thereof. This makes it possible to reduce a diameter of the pillar-shaped first-conductive-type silicon layer to be subsequently formed, to suppress short-channel effects in a transistor so as to reduce a leak current.
Alternatively, the step (a) may include the sub-steps of: forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer; forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer; forming a silicon oxide film on the silicon nitride film; applying a resist onto the silicon oxide film, forming a pattern having an inverted shape of a top of the pillar-shaped first-conductive-type silicon layer, using the resist by lithography, and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer; depositing an oxide film and etching back the oxide film to reduce a diameter of the hole penetrating through the silicon oxide film; forming an amorphous silicon or polysilicon film to fill the hole formed in the silicon oxide film; polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing; and removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask. This also makes it possible to reduce a diameter of the pillar-shaped first-conductive-type semiconductor layer to be subsequently formed, to suppress short-channel effects in a transistor so as to reduce a leak current.
In a preferred embodiment of the present invention, the step (a) includes the sub-steps of: dry-etching a silicon nitride film and a pad oxide film deposited on an initial silicon layer, using an amorphous silicon or polysilicon film-based mask serving as the second hard mask, to form a silicon nitride film-based mask serving as the first hard mask; and forming the pillar-shaped first-conductive-type silicon layer by dry etching using the first hard mask and the second hard mask. In this case, when the amorphous silicon or polysilicon film-based mask serving as the second hard mask is fully etched away to cause a change in plasma emission intensity detectable by a dry etching apparatus, a dry-etching end-point detection process can be performed by detecting the change in the plasma emission intensity, to control a height dimension of the pillar-shaped first-conductive-type silicon layer.
In a preferred embodiment of the present invention, a thickness of the amorphous silicon or polysilicon film-based mask serving as the second hard mask is less than a height dimension of the pillar-shaped first-conductive-type silicon layer. This makes it possible to effectively perform the dry-etching end-point detection process.
In a preferred embodiment of the present invention, the step (b) includes the sub-steps of: sacrificially oxidizing the pillar-shaped first-conductive-type silicon layer fabricated on the planar silicon layer to form a sacrificial oxide film as a means for reducing irregularities in a region of the sidewall of the pillar-shaped first-conductive-type silicon layer serving as a channel region, removing a silicon surface implanted with a foreign substance typified by carbon during the dry etching, and protecting the pillar-shaped first-conductive-type silicon layer from contaminations typified by-products to be produced during dry etching in a subsequent step; applying a resist onto the planar silicon layer, and forming a pattern for the second-conductive-type silicon layer to be formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, using the resist by lithography; and dry-etching the planar silicon layer to form the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then removing the resist. In this case, the oxide film formed by the sacrificial oxidation is used as a protective film for the pillar-shaped first-conductive-type silicon layer. This makes it possible to reduce the number of production steps so as to reduce a production cost.
In a preferred embodiment of the present invention, the step (b) includes introducing a second-conductive-type impurity into a surface of the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer on which there is a silicon nitride film-based mask by an impurity doping process typified by impurity implantation, using the sacrificial oxide film formed during the sacrificial oxidation of the pillar-shaped first-conductive-type silicon layer, as a screen oxide film, to form the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer. In this case, the oxide film formed by the sacrificial oxidation is used as not only a protective film for the pillar-shaped first-conductive-type silicon layer but also a screen oxide film during impurity implantation. This makes it possible to reduce the number of production steps so as to reduce a production cost.
In a preferred embodiment of the present invention, a diameter of the pillar-shaped first-conductive-type silicon layer is less than that of the silicon nitride film-based mask serving as the first hard mask. This makes it possible to prevent implantation of an imparity from the side of the sidewall of the pillar-shaped first-conductive-type silicon layer during the impurity implantation.
In a preferred embodiment of the present invention, an implantation angle during the impurity implantation for use in forming the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer is in the range of 0 to 6 degrees. This makes it possible to prevent implantation of an imparity from the side of the sidewall of the pillar-shaped first-conductive-type silicon layer during the impurity implantation.
In a preferred embodiment of the present invention, the second-conductive-type silicon layer is formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, without implanting the impurity into the upper portion of the pillar-shaped first-conductive-type silicon layer. This makes it possible to readily optimize impurity implantation conditions for the upper portion of the pillar-shaped first-conductive-type silicon layer and the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, to suppress short-channel effects in a transistor so as to reduce a leak current.
In a preferred embodiment of the present invention, the step (c) includes the sub-step of: oxidizing a silicon surface of the pillar-shaped first-conductive-type silicon layer with silicon nitride film-based mask fabricated on the planar silicon layer, and etching the silicon nitride film-based mask to reduce a diameter of the silicon nitride film-based mask to be less than that of the pillar-shaped first-conductive-type silicon layer. This makes it possible remove a part of a high-k gate dielectric film based on dry etching in a subsequent step.
In a preferred embodiment of the present invention, the step (c) includes the sub-steps of: removing the sacrificial oxide film by etching from a pillar-shaped first-conductive-type semiconductor layer with a silicon nitride film-based mask and a sacrificial oxide film formed on the planar semiconductor layer and a planar semiconductor layer having a second-conductive-type semiconductor layer formed therein, forming gate dielectric film of a high-k film such as a hafnium oxide film, and forming a metal film as a gate electrode material, to allow the pillar-shaped first-conductive-type silicon layer to be buried therein; and polishing the metal film by chemical mechanical polishing to flatten an upper surface of the gate electrode material. In this case, the silicon nitride film-based mask serving as the first hard mask can be used as a stopper for the chemical mechanical polishing to control an amount of chemical mechanical polishing with high repeatability.
In a preferred embodiment of the present invention, the step (c) includes the sub-steps of: etching back the flattened metal film serving as the gate electrode material to allow the resulting metal film to have a desired gate length of the gate electrode; and forming a silicon oxide film on respective upper surfaces of the pillar-shaped first-conductive-type semiconductor layer and the etched-back metal film serving as the gate electrode material. In this case, the silicon oxide film can cover the metal film to allow subsequent steps to be performed without taking into account metal contamination, and can protect the upper surface of the gate electrode material from a wet or dry treatment to be performed in a subsequent step, so as to suppress a change in the gate length and damage of the gate dielectric film from the side of the upper surface thereof.
In a preferred embodiment of the present invention, the step (c) includes the sub-steps of: forming a silicon nitride film on the silicon oxide film to have a film thickness derived by subtracting a film thickness of the silicon oxide film from a sum of a desired film thickness of the gate electrode and a film thickness of the gate dielectric film; etching back the silicon nitride film and the silicon oxide film to form a silicon nitride film-based sidewall and a silicon oxide film-based sidewall, wherein a sum of a film thickness of the silicon nitride film-based sidewall and a film thickness of the silicon oxide film-based sidewall which determine a sum of a film thickness of the gate electrode to be formed by the metal film and the film thickness of the gate dielectric film is controlled by adjusting a film thickness of the silicon nitride film to be formed in the sub-step of forming a silicon nitride film, and conditions for the etching-back in the sub-step of etching back the silicon nitride film, so as to allow the gate electrode to have the desired film thickness; applying a bottom antireflective coating (BARC) layer and a resist, and forming a pattern for a gate line, using the resist by lithography; and etching the BARC layer, the silicon oxide film, and the metal film serving as the gate electrode material, using the resist as a mask to form the gate electrode and the gate line. Further, the steps (d) and (e) include the sub-steps of: removing the silicon nitride film-based mask, the silicon nitride film-based sidewall and the silicon oxide film-based sidewall on an upper portion of the pillar-shaped first-conductive-type silicon layer by dry etching or wet etching; and forming a silicon oxide film and a silicon nitride film and etching back the silicon nitride film and the silicon oxide film to expose an upper surface of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and a top surface of the pillar-shaped first-conductive-type silicon layer, while forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film, on the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer and in contact with the top of the gate electrode, and forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film on the sidewall of the gate electrode. The step (f) includes introducing a second-conductive-type impurity into an upper portion of the pillar-shaped first-conductive-type silicon layer through an impurity doping process typified by impurity implantation, to form the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, and the steps (g) and (h) include subjecting each of the upper surface of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and an upper surface of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, to sputtering of a metal such as nickel (Ni) or cobalt (Co), and a heat treatment, and removing an unreacted metal film, to form the metal-semiconductor compound on each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer. In this case, the silicon oxide film-based sidewalls and the silicon nitride film-based sidewalls can serve as a means to isolate the gate electrode from each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, so as to prevent short-circuiting between the gate electrode and each of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, due to the metal-semiconductor compounds, and the silicon nitride film-based sidewall covering the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer can serve as a means to control formation of a metal-semiconductor compound from the side of the sidewall of the pillar-shaped first-conductive-type silicon layer.
In a preferred embodiment of the present invention, the steps (i) and (j) include the sub-steps of: forming a film typified by a silicon nitride film to serve as a contact stopper; forming a silicon oxide film to serve as an interlayer film and then flattening the silicon oxide film by chemical mechanical polishing; forming contact holes on respective ones of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, a gate line extending from the gate electrode, and the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, by etching. This makes it possible to reduce a resistance of each of the contacts.
In a preferred embodiment of the present invention, the sub-step of forming contact holes includes etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, and then etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away. This makes it possible to optimize etching conditions for the contact hole on the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, while optimizing etching conditions for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.
Alternatively, the sub-step of forming contact holes may include etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away. This also makes it possible to optimize etching conditions for the contact hole on the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, while optimizing etching conditions for the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.
Alternatively, the sub-step of forming contact holes may include etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away. This also makes it possible to optimize etching conditions for the contact hole on the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, while optimizing etching conditions for and the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.
Alternatively, the sub-step of forming contact holes may include etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away. This also makes it possible to optimize etching conditions for the contact hole on the contact hole on the top of the second-conductive-type silicon layer formed in the upper portion of the pillar-shaped first-conductive-type silicon layer, while optimizing etching conditions for and the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.
The semiconductor device of the present invention comprises: a planar semiconductor layer formed on a substrate, wherein the planar semiconductor layer has a second-conductive-type semiconductor layer formed therein and a metal-semiconductor compound formed on the second-conductive-type semiconductor layer; a pillar-shaped first-conductive-type semiconductor layer formed on the planar semiconductor layer, wherein the pillar-shaped first-conductive-type semiconductor layer has a second-conductive-type semiconductor layer formed in an upper portion thereof and a metal-semiconductor compound formed on the second-conductive-type semiconductor layer; a gate dielectric film formed around the pillar-shaped first-conductive-type semiconductor layer; a gate electrode made of a metal and formed to surround the gate dielectric film; a sidewall-shaped dielectric film formed on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode; and a sidewall-shaped dielectric film formed on a sidewall of the gate electrode. This makes it possible to apply different voltages to respective ones of the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, the gate electrode and the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer, and reduce a resistance of each of the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, and the second-conductive-type semiconductor layer formed in the upper portion of the pillar-shaped first-conductive-type semiconductor layer.
In a preferred embodiment of the present invention, a distance between a central axis of the pillar-shaped first-conductive-type semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped first-conductive-type semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film formed on the sidewall of the gate electrode. This makes it possible to form a metal-semiconductor compound on the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer, so that a resistance of the second-conductive-type semiconductor layer formed in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer can be reduced.
FIG. 37(a) is a top plan view of an NMOS SGT formed using the present invention, and FIG. 37(b) is a sectional view taken along the line A-A′ in FIG. 37(a). With reference to FIGS. 37(a) and 37(b), the NMOS SGT formed using the present invention will now be described.
A planar silicon layer 112 is formed on a substrate which comprises a buried oxide (BOX) layer 120 formed on a Si layer 111, and a pillar-shaped silicon layer 113 is formed on the planar silicon layer 112. A gate dielectric film 145 consisting of a high-k (high-dielectric constant) film, and a metal gate electrode 147, are formed around the pillar-shaped silicon layer 113. An N+ source diffusion layer 200 is formed in a portion of the planar silicon layer 112 underneath the pillar-shaped silicon layer, and an N+ drain diffusion layer 201 is formed in an upper portion of the pillar-shaped silicon layer. A contact 174 is formed on the N+ source diffusion layer 200, and a contact 173 is formed on the N+ drain diffusion layer 201. A contact 172 is formed on a gate line 141b extending from the gate electrode 141a. 
FIG. 38 is a sectional view taken along the line B-B′ in FIG. 37(a). In order to reduce a resistance of a source region, it is necessary to form a silicide on the source region. In this regard, as a prerequisite to allowing the silicide to be formed on the planar silicon layer 112, the following condition must be satisfied:

Wa>Wp+Wox+Wg+Ws 

, wherein Wa is a distance between a central axis of the silicon pillar 113 and a lateral end of the planar silicon layer 112. Further, Wp, Wox, Wg and Ws are a distance between the central axis and a sidewall of the silicon pillar 113, a thickness of the gate dielectric film 145, a width of the gate electrode 147, and a total width of an oxide film-based sidewall and a nitride film-based sidewall, i.e., a width of a sidewall-shaped dielectric film, respectively.

Under a condition that the N+ source diffusion layer is connected to a GND potential, and the N+ drain diffusion layer is connected to a power supply potential Vcc, a potential ranging from zero to Vcc is applied to the gate electrode to allow the SGT to operate as a transistor. In the above structure, the N+ diffusion layer formed in the upper portion of the pillar-shaped silicon layer may serve as an N+ source diffusion layer, and the N+ diffusion layer formed in the portion of the planar silicon layer underneath the pillar-shaped silicon layer may serve as an N+ drain diffusion layer.
With reference to FIGS. 1 to 37(b), an SGT production method according to one embodiment of the present invention will be described below. In FIGS. 2(a) to 37(b), the same elements or components are defined by a common reference numeral or code. FIG. 1 shows steps of the SGT production method according to this embodiment. FIGS. 2(a) to 37(b) show the SGT production method according to this embodiment, on a step-by-step basis, wherein the figure suffixed with (a) is a top plan view, and the figure suffixed with (b) is a sectional view taken along the line A-A′ in the figure suffixed with (a).
Referring to FIGS. 2(a) and 2(b), an SOI substrate is prepared which comprises a BOX layer 120 formed on a Si layer 111, and a silicon layer 110 formed on the BOX layer 120. A pad oxide film 121 is formed on the SOI layer 110. Before forming the pad oxide film (pad oxidation), an operation of forming a lot, an operation of forming a laser mark, and a pre-pad-oxidation cleaning operation, may be performed. Further, after the pad oxidation, a thickness measurement operation for the pad oxide film may be performed (Steps 1, 2, 3, 4, 5 in FIG. 1).
Subsequently, an impurity may be implanted into the SOI layer through the pad oxide film to adjust a threshold, and then the SOI layer may be subjected to annealing to activate and diffuse the impurity so as to promote uniform distribution of the impurity in the SOI layer. The pad oxide film formed to reduce a stress between the silicon and a silicon nitride film to be formed in the next step is also used as a screen oxide film during the impurity implantation, which makes it possible to reduce the number of production step so as to reduce a production cost.
Referring to FIGS. 3(a) and 3(b), a silicon nitride film 130 serving as a first hard mask is formed, and then a silicon oxide film 122 is formed. After forming the silicon nitride film, a thickness measurement operation for the nitride film may be performed. Further, after depositing the silicon oxide film, a thickness measurement operation for the silicon oxide film may be performed (Steps 6, 7, 8, 9 in FIG. 1).
Referring to FIGS. 4(a) and 4(b), a resist is applied, and a pattern having an inverted shape of a top view of a pillar-shaped silicon layer is formed using the resist by lithography. Then, a hole is formed in the silicon oxide film 122 by dry etching, in such a manner that it penetrates through the silicon oxide film 122 at a position for forming the pillar-shaped silicon layer. After the lithography, a dimension measurement operation and a verification operation may be performed. Further, after the etching, a post-etching cleaning operation may be performed (Steps 10, 11, 12, 13, 14, 15, 16, 17 in FIG. 1). Subsequently, a diameter of the hole penetrating through the silicon oxide film 122 may be reduced by depositing an oxide film 129 as shown in FIGS. 39(a) and 39(b), and etching back the oxide film 129 as shown in FIGS. 40(a) and 40(b)
Referring to FIGS. 5(a) and 5(b), an amorphous silicon or polysilicon film 140 is formed to fill the hole formed in the silicon oxide film 122. Before depositing the amorphous silicon or polysilicon, a pre-deposition cleaning operation may be performed. Further, after the deposition, a thickness measurement operation for the amorphous silicon or polysilicon film may be performed (Steps 18, 19, 20 in FIG. 1).
Referring to FIGS. 6(a) and 6(b), a portion of the amorphous silicon or polysilicon film 140 formed on the silicon oxide film 122 is polished and removed by chemical mechanical polishing (CMP). After the polishing, a thickness measurement operation for the amorphous silicon or polysilicon film may be performed (Steps 21, 22 in FIG. 1).
Referring to FIGS. 7(a) and 7(b), the silicon oxide film 122 is removed by wet etching using hydrofluoric acid or the like, or dry etching, to form an amorphous silicon or polysilicon film-based mask 140 serving as a second hard mask to be used during dry etching for the pillar-shaped silicon layer in a subsequent step (Step 23 in FIG. 1).
Referring to FIGS. 8(a) and 8(b), the amorphous silicon or polysilicon film-based mask 140 is sacrificially oxidized to form a silicon oxide film 127 thereon to reduce a size of the amorphous silicon or polysilicon film-based mask. Before the sacrificial oxidation, a pre-sacrificial-oxidation cleaning operation may be performed. Further, after the oxidation, a thickness measurement operation for the sacrificial oxide film may be performed (Steps 24, 25, 26 in FIG. 1). Based on the sacrificial oxidation, a size of the pillar-shaped silicon layer to be formed in a subsequent step can be reduced. This capability to reduce a diameter of the pillar-shaped silicon layer makes it possible to suppress short-channel effects so as to reduce a leak current.
Referring to FIGS. 9(a) and 9(b), the silicon oxide film 128 on a surface of the amorphous silicon or polysilicon film-based mask 140 is removed by wet etching using hydrofluoric acid or the like, or dry etching (Step 27 in FIG. 1).
Referring to FIGS. 10(a) and 10(b), the silicon nitride film (first hard mask) 130 and the pad oxide film 121 are dry-etched using the amorphous silicon or polysilicon film-based mask (second hard mask) 140 (Steps 28, 29 in FIG. 1).
Referring to FIGS. 11(a) and 11(b), the pillar-shaped silicon layer 113 is formed by dry etching using the silicon nitride film-based mask (first hard mask) 130 and the amorphous silicon or polysilicon film-based mask (second hard mask) 140. After the etching, an organic-substance removal operation, a scanning electron microscopic (SEM) inspection operation, and a step-height verification operation, may be performed (Steps 30, 31, 32, 33 in FIG. 1). During the etching, the amorphous silicon or polysilicon film-based mask (second hard mask) 140 is also etched. When the amorphous silicon or polysilicon film-based mask 140 is fully etched away, a plasma emission intensity detectable by a dry etching apparatus is changed. Thus, an etching end-point detection can be performed by detecting the change in the plasma emission intensity. This makes it possible to stably control a height dimension of the pillar-shaped silicon layer 113 without relying on an etching rate.
As a prerequisite to the use of the end-point detection process, it is necessary that the amorphous silicon or polysilicon film-based mask 140 before the dry etching for the pillar-shaped silicon layer is formed to have a film thickness less than the height dimension of the pillar-shaped silicon layer. In this step, a continuous planar silicon layer 112 is formed on the buried oxide layer 120.
Referring to FIGS. 12(a) and 12(b), in order to reduce irregularities in a region of the sidewall of the pillar-shaped silicon layer 113 serving as a channel region, and remove a silicon surface implanted with carbon and others during the dry etching, respective surfaces of the pillar-shaped silicon layer 113 and the continuous planar silicon layer 112 are sacrificially oxidized and formed as a sacrificial oxide film 123. Before the sacrificial oxidation, a pre-sacrificial-oxidation cleaning operation may be performed. Further, after the sacrificial oxidation, a thickness measurement operation for the sacrificial oxide film may be performed (Steps 34, 35, 36 in FIG. 1).
Referring to FIGS. 13(a) and 13(b), a resist 150 is applied, and a pattern for a source diffusion layer is formed using the resist by lithography. After the lithography, an overlay-error measurement operation, a dimension measurement operation and a verification operation may be performed (Steps 37, 38, 39, 40, 41 in FIG. 1). The sacrificial oxide film 123 formed on the pillar-shaped silicon layer 113 and the continuous planar silicon layer 112 by the sacrificial oxidation will protect surfaces of the silicon layers from contamination due to by-products to be produced during dry etching in the next step, etc.
Referring to FIGS. 14(a) and 14(b), the continuous planar silicon layer 112 is dry-etched to isolate a planar silicon layer 112 from other elements (Steps 42, 43 in FIG. 1).
Referring to FIGS. 15(a) and 15(b), the resist is removed. After the removal, an organic-substance removal operation, an SEM inspection operation, and a step-height verification operation, may be performed (Steps 44, 45, 46 in FIG. 1).
Referring to FIGS. 16(a) and 16(b), an impurity, such as phosphorus (P) or arsenic (As), is introduced into the surface of the planar silicon layer 112 by impurity implantation or the like, to form an N+ source diffusion layer 200 in the planar silicon layer 112 (Steps 47, 48 in FIG. 1). In this step, the sacrificial oxide film 123 formed during the sacrificial oxidation of the pillar-shaped silicon layer 113 and the continuous planar silicon layer 112 is used as a screen oxide film, which makes it possible to reduce the number of production steps. If an impurity is implanted from the sidewall of the pillar-shaped silicon layer 113 during the implantation, it becomes a factor causing a variation in transistor characteristics. Therefore, it is essential that a width (Wp1, Wp2) of the pillar-shaped silicon layer 113 is less than a width Wn of the nitride film 130, wherein Wp1 is a width of a bottom of the pillar-shaped silicon layer, and Wp2 is a width of a top of the pillar-shaped silicon layer.
Preferably, the impurity is implanted at a small angle, specifically, at an angle ranging from zero to 6 degrees, to prevent the impurity from being implanted from the sidewall of the pillar-shaped silicon layer 113 during the implantation. In this step, no impurity is implanted into an upper portion of the pillar-shaped silicon layer 113 due to the presence of the silicon nitride film 130 formed on the pillar-shaped silicon layer 113. Preferably, the implantation for the N+ source diffusion layer 200 is performed at an angle of zero degree. Differently, an impurity implantation for a drain diffusion layer to be formed in an upper portion of the pillar-shaped silicon layer 113 in a subsequent step is preferably performed at a certain angle, because the drain diffusion layer is formed in a self-alignment manner using a gate electrode. As above, the respective implantation for the source diffusion layer to be formed in the planar silicon layer and the drain diffusion layer to be formed in the upper portion of the pillar-shaped silicon layer are performed separately, so that conditions for the respective implantations can be easily optimized. This makes it possible to suppress short-channel effects so as to reduce a leak current.
Referring to FIGS. 17(a) and 17(b), the surface of the silicon layer is oxidized to form an oxide film 124 thereon, and then a width of the nitride film 130 is reduced by wet etching. Before the oxidation, a pre-oxidation cleaning operation may be performed. Further, after the oxidation, a thickness measurement operation for the oxide film may be performed (Steps 49, 50, 51, 52 in FIG. 1). This step is performed as a pre-treatment for removing a part of a high-k gate dielectric film by dry etching in a subsequent step illustrated in FIGS. 22(a) and 22(b). Thus, in this step, the width Wn of the nitride film 130 has to be reduced to become less than the width (Wp1, Wp2) of the silicon pillar 113.
Referring to FIGS. 18(a) and 18(b), the sacrificial oxide film 123 and the oxide film 124 are removed by wet etching using hydrofluoric acid or the like (Step 53 in FIG. 1).
Referring to FIGS. 19(a) and 19(b), a HfSiO or HfSiON film is formed as a high-k gate dielectric film 145. Before forming the gate dielectric film, a pre-gate-formation cleaning operation may be performed. Further, after forming the gate dielectric film, a heat treatment operation may be performed (Steps 54, 55, 56 in FIG. 1).
Referring to FIGS. 20(a) and 20(b), a metal film 147 is formed as a gate conductive film to allow the pillar-shaped silicon layer 113 to be buried therein (Step 57 in FIG. 1).
Referring to FIGS. 21(a) and 21(b), the metal film 147 is polished by chemical mechanical polishing (CMP) to flatten an upper surface of the gate conductive film. The silicon nitride film (first hard mask) 130 is used as a CMP stopper during the CMP, which makes it possible to control an amount of CMP with high repeatability (Step 58 in FIG. 1).
Referring to FIGS. 22(a) and 22(b), the flattened metal film 147 serving as the gate dielectric film is etched back to set a gate length. During this step, the high-k gate dielectric film is also etched (Step 59 in FIG. 1). After the etching back of the metal film, a thickness measurement operation for the metal film may be performed (Step 60 in FIG. 1).
Referring to FIGS. 23(a) and 23(b), a silicon oxide film 125 is formed on respective surfaces of the silicon pillar 113 and the metal film 147 serving as the gate conductive film. The silicon oxide film 125 can cover the metal film 147, which makes it possible to allow subsequent steps to be performed without taking into account metal contamination. Further, the silicon oxide film 125 can protect the upper surface of the gate conductive film from a wet or dry treatment to be performed in a subsequent step, which makes it possible to suppress a change in the gate length, i.e., variation in the gate length, and damage of the gate dielectric film 145 from the side of the upper surface of the gate conductive film (Step 61 in FIG. 1).
Referring to FIGS. 24(a) and 24(b), a silicon nitride film 131 is formed to have a film thickness greater than a desired film thickness of a gate electrode. After forming the silicon nitride film, a thickness measurement operation for the silicon nitride film may be performed (Steps 62, 63 in FIG. 1).
Referring to FIGS. 25(a) and 25(b), the silicon nitride film 131 is etched back to form a silicon nitride film-based sidewall 131. During the etching-back, the silicon oxide film 125 is also etched. After the etching-back, an organic-substance removal operation and a configuration measurement operation may be performed (Steps 64, 65, 66 in FIG. 1). A sum of a film thickness of the silicon nitride film-based sidewall 131 and a film thickness of the silicon oxide film 125 determines a sum of a film thickness of the high-k gate dielectric film and a film thickness of a gate electrode to be formed by the metal film 147. Thus, a film thickness of the silicon nitride film 131 to be formed in the preceding step, and conditions for the etching-back in this step, are adjusted to allow the gate electrode to have a desired film thickness.
Referring to FIGS. 26(a) and 26(b), a bottom antireflective coating (BARC) layer 161 and a resist 160 are applied, and a pattern for a gate line is formed using the resist 160 by lithography. After forming the pattern, an overlay-error measurement operation, a dimension measurement operation and a verification operation may be performed (Steps 67, 68, 69, 70, 71 in FIG. 1).
Referring to FIGS. 27(a) and 27(b), the BARC layer 161, the metal film 147 serving as the gate conductive film, and the high-k gate dielectric film, are etched using the resist 160 as a mask to form a gate electrode 141a and a gate line 141b, and then the resist and the remaining BARC layer are removed. After the etching, a configuration measurement operation may be performed (Steps 72, 73, 74, 75, 76 in FIG. 1).
Referring to FIGS. 28(a) and 28(b), the silicon nitride film 130, the silicon nitride film-based sidewall 131 and the silicon oxide films 121, 125 on an upper portion of the pillar-shaped silicon layer 113, and a portion of the oxide film 124 on an upper surface of the planar silicon layer, are removed by dry etching or wet etching (Step 77 in FIG. 1).
Referring to FIGS. 29(a) and 29(b), a silicon oxide film 127 and a silicon nitride film 132 are formed. After the film formation, a thickness measurement operation for the silicon nitride film may be performed (Steps 78, 79, 80 in FIG. 1).
Referring to FIGS. 30(a) and 30(b), the silicon nitride film 132 is etched back to expose an upper surface of the N+ source diffusion layer 200 and a top surface of the pillar-shaped silicon layer 113, while covering a sidewall of the gate 147 by a silicon nitride film (dielectric film-based sidewall) 133, and covering a sidewall of the pillar-shaped silicon layer 113 by a silicon nitride film (dielectric film-based sidewall) 134. After the etching, an organic-substance removal operation and a configuration measurement operation may be performed (Steps 81, 82, 83 in FIG. 1). The nitride films 133, 134 isolate between the gate electrode 147 and each of the source diffusion layer 200 and an N+ drain diffusion layer to be subsequently formed in an upper portion of the pillar-shaped silicon layer. This makes it possible to prevent short-circuiting between the gate electrode 147 and each of the source diffusion layer 200 and the after-mentioned drain diffusion layer. In addition, the nitride film 134 covering an upper region of the sidewall of the pillar-shaped silicon layer 113 makes it possible to control silicidation from the side of the sidewall of the pillar-shaped silicon layer 113. If a silicon oxide film is used as substitute for the silicon nitride films 133, 134, it will be etched by hydrofluoric acid to be used in a cleaning/stripping operation and a pretreatment for silicidation. Thus, it is preferable to use a film insoluble in hydrofluoric acid, such as a silicon nitride film.
Referring to FIGS. 31(a) and 31(b), an impurity, such as P or As, is introduced into an upper portion of the pillar-shaped silicon layer 113 by impurity implantation or the like, to form an N+ drain diffusion layer 201 therein. After the impurity introduction, an operation of activating the impurity may be performed (Step 84, 85 in FIG. 1).
Referring to FIGS. 32(a) and 32(b), each of the upper surfaces of the source diffusion layer 200 and the drain diffusion layer 201 is transformed into a metal-semiconductor compound, i.e., silicided, by undergoing sputtering of a metal, such as nickel (Ni) or cobalt (Co), and a heat treatment, and then removing an unreacted metal film. In this manner, a silicide layer 152 and a silicide layer 153 are formed on the drain diffusion layer 201 and the source diffusion layer 200, respectively. Before forming the silicide layers, an oxide-film stripping operation may be performed (Steps 86, 87, 88, 89 in FIG. 1).
Referring to FIGS. 33(a) and 33(b), a film, such as a silicon nitride film, is formed as a contact stopper 135 (Step 90 in FIG. 1).
Referring to FIGS. 34(a) and 34(b), a silicon oxide film is formed as an interlayer film 126, and then flattened by CMP. After forming the silicon oxide film, a thickness measurement operation for the silicon oxide film may be performed. Further, after the flattening, a thickness measurement operation for the silicon oxide film and the silicon nitride films may be performed (Steps 91, 92, 93, 94, 95 in FIG. 1).
Referring to FIGS. 35(a) and 35(b), three contact holes are formed, respectively, on the drain diffusion layer 201 in the upper portion of the pillar-shaped silicon layer 113, the gate line 147b and the source diffusion layer 200, by etching. Before the etching for the contact holes, a lithographic exposure operation using a contact mask is performed. Then, a dimension measurement operation, an overlay-error measurement operation and a verification operation may be further performed. Further, after forming the contact holes, a plasma-based resist stripping operation is performed. After the plasma peeling, a post-contact-etching cleaning operation, a dimension measurement operation, a thickness measurement operation for the oxide film, a verification operation, and a wafer container replacement operation, may be performed (Steps 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108 in FIG. 1).
Respective etching depths of the contact hole on a top of the pillar-shaped silicon layer, the contact hole on the gate line, and the contact hole on the portion of the planar silicon layer underneath the pillar-shaped silicon layer, are different from each other. Thus, the etching for the contacts may be performed as follows. As shown in FIGS. 41(a) and 41(b), portions of the interlayer film for the contact hole on the top of the pillar-shaped silicon layer and the contact hole on the gate line are etched. Then, as shown in FIGS. 42(a) and 42(b), a portion of the interlayer film for the contact hole on the portion of the planar silicon layer underneath the pillar-shaped silicon layer is etched using a resist 162 as a mask. After the etching of the interlayer film, the contact stopper is etched.
Alternatively, the three contact holes may be formed by etching a portion of the interlayer film for the contact hole on the top of the pillar-shaped silicon layer, as shown in FIGS. 43(a) and 43(b), and then etching portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the planar silicon layer underneath the pillar-shaped silicon layer, as shown in FIGS. 44(a) and 44(b). In this case, the contact stopper may also be etched after the etching of the interlayer film.
As above, the etching of the portion of the interlayer film for the contact hole on the top of the pillar-shaped silicon layer is performed separately from the etching of the portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the planar silicon layer underneath the pillar-shaped silicon layer. This makes it possible to optimize etching conditions for the contact hole on the top of the pillar-shaped silicon layer, while optimizing etching conditions for the contact hole on the gate line and the contact hole on the portion of the planar silicon layer underneath the pillar-shaped silicon layer.
Referring to FIGS. 36(a) and 36(b), a film 171 made of a barrier metal, such as tantalum (Ta) or tantalum nitride (TaN), is formed on each of the contact holes. Then, a copper (Cu) film 170 is formed thereon by sputtering or plating, and subjected to CMP to form three contacts 172, 173, 174. As the barrier metal, titanium (Ti) or titanium nitride (TiN) may be used. Tungsten (W) may also be used. Alternatively, an alloy containing copper may be used. After the film formation, an under-surface surface treatment operation, a verification operation and a heat treatment operation may be performed. Further, after the CMP, a verification operation may be performed (Steps 109, 110, 111, 112, 113, 114, 115 in FIG. 1).
Referring to FIGS. 37(a) and 37(b), a silicon carbide (SiC) film 180 is formed as an etching stopper for first-layer interconnection lines, and then a low-k film 190 is formed as an interlayer film of a first interconnection layer. After the film formation, a thickness measurement operation for the low-k film and a verification operation may be performed (Steps 116, 117, 118, 119 in FIG. 1). Then, a patterning for the first-layer interconnection lines is performed, and a trench pattern is formed in the first interconnection layer. After the patterning, a dimension measurement operation, an overlay-error measurement operation and a verification operation may be performed. Further, after forming the trench pattern, a plasma-based resist stripping operation and a verification operation may be performed (Steps 120, 121, 122, 123, 124, 125, 126, 127 in FIG. 1). Subsequently, a film 175 made of a barrier metal, such as Ta or TaN, is formed on each of the trenches. Then, a Cu film 176 is formed thereon by sputtering or plating, and subjected to CMP to form the first-layer interconnection lines 177, 178, 179. As the barrier metal, titanium (Ti) or titanium nitride (TiN) may be used. Tungsten (W) may also be used. Alternatively, an alloy containing copper may be used. After the film formation, an under-surface surface treatment operation, a verification operation and a heat treatment operation may be performed. Further, after the CMP, a verification operation may be performed (Steps 128, 129, 130, 131, 132, 133, 134 in FIG. 1).
Then, a nitride-film deposition operation, and an interlayer-dielectric-film deposition operation and a thickness measurement operation for the interlayer dielectric film may be performed (Steps 135, 136, 137 in FIG. 1). Further, a lithographic exposure operation using a pad-via mask, a dimension measurement operation, an overlay-error measurement operation, a verification operation, a pad-via etching operation, a plasma-based resist stripping operation, a post-etching cleaning operation, a dimension measurement operation, a thickness measurement operation for an oxide film, a verification operation, a pre-metalization cleaning operation, a wafer-container replacement operation, an aluminum deposition operation, an under-surface treatment operation, a lithographic exposure operation for pad aluminum, an overlay-error measurement operation, a dimension measurement operation, a verification operation, a pad-aluminum etching operation, a plasma-based resist stripping operation, a post-metal-etching cleaning operation, an optical inspection operation, an SEM inspection operation, a thickness measurement operation for the oxide film, an operation of depositing a dielectric film, a thickness measurement operation for the dielectric film, a lithographical exposure operation for the dielectric film, an optical inspection operation, an operation of etching the dielectric film, a plasma-based resist stripping operation, an operation of cleaning the dielectric film, a verification operation, and a heat treatment operation, may be performed (Steps 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177 in FIG. 1).
Before the operation for the pad-via, multilayer interconnection may be performed.

## Claims

1. A method of producing a semiconductor device, comprising the steps of:
(a) forming a planar semiconductor layer on a substrate and then forming a pillar-shaped first-conductive-type semiconductor layer on the planar semiconductor layer;
(b) forming a second-conductive-type semiconductor layer in a portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer;
(c) forming a gate dielectric film in contact with the pillar-shaped first-conductive-type semiconductor layer and forming a gate electrode comprising a metal around the pillar-shaped first-conductive-type semiconductor layer and overlying the gate dielectric film;
(d) forming a sidewall-shaped dielectric film in contact with the gate dielectric film at an interface on an upper region of a sidewall of the pillar-shaped first-conductive-type semiconductor layer and in contact with a top of the gate electrode;
(e) forming a sidewall-shaped dielectric film on a sidewall of the gate electrode;
(f) forming a second-conductive-type semiconductor layer in an upper portion of the pillar-shaped first-conductive-type semiconductor layer;
(g) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer;
(h) forming a metal-semiconductor compound on the second-conductive-type semiconductor layer in the upper portion of the pillar-shaped first-conductive-type semiconductor layer;
(i) forming a contact on the second-conductive-type semiconductor layer in the portion of the planar semiconductor layer underneath the pillar-shaped first-conductive-type semiconductor layer; and
(j) forming a contact on the second-conductive-type semiconductor layer in the upper portion of the pillar-shaped first-conductive-type semiconductor layer.

2. The method as defined in claim 1, wherein a distance between a central axis of the pillar-shaped first-conductive-type semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped first-conductive-type semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film on the sidewall of the gate electrode.

3. The method as defined in claim 1, wherein:
the planar semiconductor layer is a planar silicon layer;
the first-conductive-type semiconductor layer is a first-conductive-type silicon layer; and
each of the second-conductive-type semiconductor layers is a second-conductive-type silicon layer.

4. The method as defined in claim 3, wherein:
the planar semiconductor layer is a planar silicon layer;
the first-conductive-type semiconductor layer is a p-type silicon layer or a non-doped silicon layer; and
each of the second-conductive-type semiconductor layers is an n-type silicon layer.

5. The method as defined in claim 3, wherein:
the planar semiconductor layer is a planar silicon layer;
the first-conductive-type semiconductor layer is an n-type silicon layer or a non-doped silicon layer; and
each of the second-conductive-type semiconductor layers is a p-type silicon layer.

6. The method as defined in claim 3, wherein the step (a) includes the sub-steps of:
forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer;
implanting an impurity into the initial silicon layer through the pad oxide film to adjust a threshold, and then subjecting the initial silicon layer to annealing to activate and diffuse the impurity so as to promote uniform distribution of the impurity in the initial silicon layer; and
forming a silicon nitride film for use as a mask during formation of the pillar-shaped first-conductive-type silicon layer.

7. The method as defined in claim 3, wherein the step (a) includes the sub-step of:
forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer;
forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer;
forming a silicon oxide film on the silicon nitride film;
applying a resist onto the silicon oxide film, forming a pattern having an inverted shape of a top view of the pillar-shaped first-conductive-type silicon layer, using the resist, and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer;
forming an amorphous silicon or polysilicon film to fill the hole in the silicon oxide film;
polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing;
removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask;
sacrificially oxidizing the amorphous silicon or polysilicon film-based mask to reduce a size of the amorphous silicon or polysilicon film-based mask; and
etching the amorphous silicon or polysilicon film-based mask to remove the sacrificial silicon oxide film on a surface thereof.

8. The method as defined in claim 3, wherein the step (a) includes the sub-step of:
forming, on the substrate, an initial silicon layer for forming therefrom the pillar-shaped first-conductive-type silicon layer and the planar silicon layer, and then forming a pad oxide film on the initial silicon layer;
forming a silicon nitride film for use as a first hard mask during formation of the pillar-shaped first-conductive-type silicon layer;
forming a silicon oxide film on the silicon nitride film;
applying a resist onto the silicon oxide film, forming a pattern having an inverted shape with respect to a top view of the pillar-shaped first-conductive-type silicon layer, using the resist and forming a hole in the silicon oxide film to penetrate through the silicon oxide film at a position for forming the pillar-shaped first-conductive-type silicon layer;
depositing an oxide film and etching back the oxide film to reduce a diameter of the hole penetrating through the silicon oxide film;
forming an amorphous silicon or polysilicon film to fill the hole in the silicon oxide film;
polishing and removing a portion of the amorphous silicon or polysilicon film on the silicon oxide film by chemical mechanical polishing; and
removing the silicon oxide film by etching, to form an amorphous silicon or polysilicon film-based mask serving as a second hard mask.

9. The method as defined in claim 3, wherein the step (a) includes the sub-steps of:
dry-etching a silicon nitride film and a pad oxide film deposited on an initial silicon layer, using an amorphous silicon or polysilicon film-based mask serving as the second hard mask, to form a silicon nitride film-based mask serving as the first hard mask;
forming the pillar-shaped first-conductive-type silicon layer by dry etching using the first hard mask and the second hard mask; and
when the amorphous silicon or polysilicon film-based mask serving as the second hard mask is fully etched away to cause a change in plasma emission intensity detectable by a dry etching apparatus, performing a dry-etching end-point detection process by detecting the change in the plasma emission intensity, to control a height dimension of the pillar-shaped first-conductive-type silicon layer.

10. The method as defined in claim 9, wherein a thickness of the amorphous silicon or polysilicon film-based mask serving as the second hard mask is less than a height dimension of the pillar-shaped first-conductive-type silicon layer.

11. The method as defined in claim 3, wherein the step (b) includes the sub-steps of:
sacrificially oxidizing the pillar-shaped first-conductive-type silicon layer fabricated on the planar silicon layer to form a sacrificial oxide film as a means for reducing irregularities in a region of the sidewall of the pillar-shaped first-conductive-type silicon layer serving as a channel region, removing a silicon surface implanted with a foreign substance typified by carbon during the dry etching, and protecting the pillar-shaped first-conductive-type silicon layer from contaminations typified by by-products to be produced during dry etching in a subsequent step;
applying a resist onto the planar silicon layer, and forming a pattern for the second-conductive-type silicon layer to be formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer; and
dry-etching the planar silicon layer to form the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then removing the resist.

12. The method as defined in claim 11, wherein a diameter of the pillar-shaped first-conductive-type silicon layer is less than that of the silicon nitride film-based mask serving as the first hard mask.

13. The method as defined in claim 3, wherein the step (b) includes introducing a second-conductive-type impurity into a surface of the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer on which there is a silicon nitride film-based mask by an impurity doping process typified by impurity implantation, using the sacrificial oxide film formed during the sacrificial oxidation of the pillar-shaped first-conductive-type silicon layer, as a screen oxide film, to form the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer.

14. The method as defined in claim 3, wherein an implantation angle during an impurity implantation for use in forming the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer is in the range of 0 to 6 degrees.

15. The method as defined in claim 3, wherein the second-conductive-type silicon layer is formed in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, without implanting an impurity into the upper portion of the pillar-shaped first-conductive-type silicon layer.

16. The method as defined in claim 3, wherein the step (c) includes the sub-step of oxidizing a silicon surface of the pillar-shaped first-conductive-type silicon layer with silicon nitride film-based mask fabricated on the planar silicon layer, and etching the silicon nitride film-based mask to reduce a diameter of the silicon nitride film-based mask to be less than that of the pillar-shaped first-conductive-type silicon layer, so as to allow a part of a high-k gate dielectric film to be removed based on dry etching in a subsequent step.

17. The method as defined in claim 3, wherein the step (c) includes the sub-steps of:
removing the sacrificial oxide film by etching from a pillar-shaped first-conductive-type semiconductor layer with a silicon nitride film-based mask and a sacrificial oxide film formed on the planar semiconductor layer and a planar semiconductor layer having a second-conductive-type semiconductor layer formed therein, forming gate dielectric film of a high-k film such as a hafnium oxide film, and forming a metal film as a gate electrode material, to allow the pillar-shaped first-conductive-type silicon layer to be buried therein; and
polishing the metal film by chemical mechanical polishing to flatten an upper surface of the gate electrode material, wherein the silicon nitride film-based mask serving as the first hard mask is used as a stopper for the chemical mechanical polishing to control an amount of chemical mechanical polishing with high repeatability.

18. The method as defined in claim 17, wherein the step (c) includes the sub-steps of:
etching back the flattened metal film serving as the gate electrode material to allow the resulting metal film to have a desired gate length of the gate electrode; and
forming a silicon oxide film on respective upper surfaces of the pillar-shaped first-conductive-type semiconductor layer and the etched-back metal film serving as the gate electrode material, wherein the silicon oxide film covers the metal film to allow subsequent steps to be performed without taking into account metal contamination, and protects the upper surface of the gate electrode material from a wet or dry treatment to be performed in a subsequent step, so as to suppress a change in the gate length and damage of the gate dielectric film from the side of the upper surface thereof.

19. The method as defined in claim 18, wherein the step (c) includes the sub-steps of:
forming a silicon nitride film on the silicon oxide film to have a film thickness derived by subtracting a film thickness of the silicon oxide film from a sum of a desired film thickness of the gate electrode and a film thickness of the gate dielectric film;
etching back the silicon nitride film and the silicon oxide film to form a silicon nitride film-based sidewall and a silicon oxide film-based sidewall, wherein a sum of a film thickness of the silicon nitride film-based sidewall and a film thickness of the silicon oxide film-based sidewall which determine a sum of a film thickness of the gate electrode to be formed by the metal film and the film thickness of the gate dielectric film is controlled by adjusting a film thickness of the silicon nitride film to be formed in the sub-step of forming a silicon nitride film, and conditions for the etching-back in the sub-step of etching back the silicon nitride film, so as to allow the gate electrode to have the desired film thickness;
applying a bottom antireflective coating (BARC) layer and a resist, and forming a pattern for a gate line; and
etching the BARC layer, the silicon oxide film, and the metal film serving as the gate electrode material, using the resist as a mask to form the gate electrode and the gate line;

the steps (d) and (e) include the sub-steps of:
removing the silicon nitride film-based mask, the silicon nitride film-based sidewall and the silicon oxide film-based sidewall on an upper portion of the pillar-shaped first-conductive-type silicon layer by dry etching or wet etching; and
forming a silicon oxide film and a silicon nitride film and etching back the silicon nitride film and the silicon oxide film to expose an upper surface of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and a top surface of the pillar-shaped first-conductive-type silicon layer, while forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film, on the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer and in contact with the top of the gate electrode, and forming a silicon oxide film-based sidewall and a silicon nitride film-based sidewall serving as the sidewall-shaped dielectric film on the sidewall of the gate electrode;

the step (f) includes introducing a second-conductive-type impurity into an upper portion of the pillar-shaped first-conductive-type silicon layer through an impurity doping process typified by impurity implantation, to form the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer; and
the steps (g) and (h) include subjecting each of the upper surface of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and an upper surface of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, to sputtering of a metal such as nickel (Ni) or cobalt (Co), and a heat treatment, and removing an unreacted metal film, to form the metal-semiconductor compound on each of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer,
and wherein: the silicon oxide film-based sidewalls and the silicon nitride film-based sidewalls serve as a means to isolate the gate electrode from each of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, so as to prevent short-circuiting between the gate electrode and each of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer and the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, due to the metal-semiconductor compounds; and
the silicon nitride film-based sidewall covering the upper region of the sidewall of the pillar-shaped first-conductive-type silicon layer serves as a means to control formation of a metal-semiconductor compound from the side of the sidewall of the pillar-shaped first-conductive-type silicon layer.

20. The method as defined in claim 3, wherein the steps (i) and (j) include the sub-steps of:
forming a film typified by a silicon nitride film to serve as a contact stopper;
forming a silicon oxide film to serve as an interlayer film and then flattening the silicon oxide film by chemical mechanical polishing;
forming contact holes on respective ones of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, a gate line extending from the gate electrode, and the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, by etching.

21. The method as defined in claim 20, wherein the sub-step of forming contact holes includes etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, and then etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.

22. The method as defined in claim 20, wherein the sub-step of forming contact holes includes etching a portion of the interlayer film for the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer and the contact hole on the gate line, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.

23. The method as defined in claim 20, wherein the sub-step of forming contact holes includes etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, and then etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.

24. The method as defined in claim 20, wherein the sub-step of forming contact holes includes etching respective portions of the interlayer film for the contact hole on the gate line and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, and then etching a portion of the interlayer film for the contact hole on a top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, whereafter respective portions of the contact stopper corresponding to the contact hole on the top of the second-conductive-type silicon layer in the upper portion of the pillar-shaped first-conductive-type silicon layer, the contact hole on the gate line, and the contact hole on the portion of the second-conductive-type silicon layer in the portion of the planar silicon layer underneath the pillar-shaped first-conductive-type silicon layer, are etched away.

25. A semiconductor device comprising:
a planar semiconductor layer on a substrate, the planar semiconductor layer having a semiconductor region of opposite conductivity therein and a metal-semiconductor compound on the semiconductor region;
a pillar-shaped semiconductor layer on the planar semiconductor layer, the pillar-shaped semiconductor layer having a diffusion region in an upper portion thereof and a metal-semiconductor compound on the diffusion region, the diffusion region having a conductivity opposite to that of the pillar-shaped semiconductor layer;
a gate dielectric film in contact with the pillar-shaped semiconductor layer;
a gate electrode comprising a metal overlying the gate dielectric film;
a sidewall-shaped dielectric film in contact with the gate dielectric film at an interface on an upper region of a sidewall of the pillar-shaped semiconductor layer and in contact with a top of the gate electrode; and
a sidewall-shaped dielectric film on a sidewall of the gate electrode.

26. The semiconductor device as defined in claim 25, wherein a distance between a central axis of the pillar-shaped semiconductor layer and a lateral end of the planar semiconductor layer is greater than a sum of: a distance between the central axis and the sidewall of the pillar-shaped semiconductor layer; a thickness of the gate dielectric film; a thickness of the gate electrode; and a thickness of the sidewall-shaped dielectric film on the sidewall of the gate electrode.