Semiconductor material, a semiconductor device using the same, and a manufacturing method thereof

A method of manufacturing a semiconductor includes the steps of: forming a first semiconductor film on a substrate having an insulating surface; applying an energy to the first semiconductor film to crystallize the first semiconductor film; patterning the first semiconductor film to form a region that forms a seed crystal; etching the seed crystal to selectively leave a predetermined crystal face in the seed crystal; covering the seed crystal to form a second semiconductor film; and applying an energy to the second semiconductor film to conduct a crystal growth from the seed crystal in the second semiconductor film.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a technique by which a crystalline silicon 
film having a monocrystal-like region or a substantially monocrystal-like 
region is formed on a substrate having an insulating surface made of glass 
or the like. Also, the present invention relates to a technique by which a 
thin-film semiconductor device represented by a thin-film transistor is 
formed by using the crystalline silicon film. 
2. Description of the Related Art 
In the recent years, attention has been directed to a technique by which a 
thin-film transistor is constituted by using a thin-film silicon 
semiconductor film (a thickness of about several hundred to several 
thousand .ANG.) which is formed on a substrate having a glass substrate or 
an insulating surface. What the thin-film transistor is applied to with 
the most expectancy is an active matrix type liquid-crystal display unit. 
The active matrix type liquid-crystal display unit is structured such that 
liquid crystal is interposed between a pair of glass substrates and held 
therebetween. Also, it is structured such that a thin-film transistor is 
disposed on each of pixel electrodes which are arranged in the form of a 
matrix of several hundred.times.several hundred. Such structures require a 
technique by which the thin-film transistor is formed on a glass 
substrate. 
In the formation of the thin-film transistor on the glass substrate, it is 
necessary to form a thin-film semiconductor for constituting the thin-film 
transistor on the glass substrate. For the thin-film semiconductor formed 
on the glass substrate, an amorphous silicon film formed through the 
plasma CVD technique or the low pressure thermal CVD technique is 
generally utilized. 
Under existing circumstances, the thin-film transistor using the amorphous 
silicon film is practically used. However, in order to obtain display with 
a higher image quality, there is demanded a thin-film transistor utilizing 
a silicon semiconductor thin film (called "a crystalline silicon film") 
with a crystalline property. 
Techniques disclosed in Japanese Patent Unexamined Publication No. 6-232059 
and Japanese Patent Unexamined Publication No. 6-244103 made by the 
present applicant have been well known as a method of forming the 
crystalline silicon film on the glass substrate. The techniques disclosed 
in those publications are that a crystalline silicon film is formed on a 
glass substrate through a heat treatment under a heating condition which 
can be withstood by the glass substrate, that is, approximately at 
550.degree. C. for 4 hours, by utilizing a metal element that promotes the 
crystallization of silicon. 
However, the crystalline silicon film obtained by the method using the 
above-mentioned techniques is not available to a thin-film transistor that 
constitutes a variety of arithmetic operating circuits, memory circuits or 
the like. This is because its crystalline property is insufficient and a 
characteristic as required is not obtained. 
As the peripheral circuits of the active matrix type liquid-crystal display 
unit or the passive type liquid-crystal display unit, there are required a 
drive circuit for driving a thin-film transistor disposed in a pixel 
region, a circuit for dealing with or controlling a video signal, a memory 
circuit for storing a variety of information, etc. 
Of those circuits, the circuit for dealing with or controlling a video 
signal and the memory circuit for storing a variety of information are 
required to provide a performance equal to that of an integrated circuit 
using a known monocrystal wafer. Hence, when those circuits are to be 
integrated using the thin-film semiconductor formed on the glass 
substrate, the crystalline silicon film having the crystalline property 
equal to that of monocrystal must be formed on the glass substrate. 
As a method of enhancing the crystalline property of the crystalline 
silicon film, there have been proposed that the obtained crystalline 
silicon film is subjected to a re-heating treatment or to the irradiation 
of a laser beam. However, it has been proved that, even though the heat 
treatment or the irradiation of a laser beam is repeatedly conducted, it 
is difficult to dramatically improve the crystalline property. 
Also, a technique in which a monocrystal silicon thin film is obtained by 
using the SOI technique has now been researched. However, since the 
monocrystal silicon substrate cannot be utilized for the liquid-crystal 
display unit, the above technique cannot be applied directly to the 
liquid-crystal display unit. In particular, in the case of using a 
monocrystal wafer, it is difficult to apply the SOI technique to the 
liquid-crystal display unit having a large area a demand of which is 
expected to increase in the future because of a limited substrate area. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above problems, and 
therefore an object of the present invention is to provide a technique in 
which a monocrystal or monocrystal-like region is formed on a substrate 
having an insulating surface, in particular, on a glass substrate, and a 
thin-film semiconductor device represented by a thin-film transistor is 
formed by using that region. 
In order to solve the above-mentioned problems, according to one aspect of 
the present invention, there is provided a method of manufacturing a 
semiconductor, comprising the steps of: 
forming a first semiconductor film on a substrate having an insulating 
surface; 
applying an energy to said first semiconductor film to crystallize said 
first semiconductor film; 
patterning said first semiconductor film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal 
surface in said seed crystal; 
covering said seed crystal to form a second semiconductor film; and 
applying an energy to said second semiconductor film to conduct a crystal 
growth from said seed crystal in said second semiconductor film. 
In the above-mentioned structure, a silicon film is typically used for the 
first and second semiconductor films. Also, in general, an amorphous 
silicon film formed through the CVD technique is used for the silicon 
film. 
The reason why the predetermined crystal surface is selectively left is to 
conduct the crystal growth so as to produce crystal more approximating 
monocrystal. Leaving the predetermined crystal surface may be achieved by 
using etching means having a selectivity with respect to the predetermined 
crystal surface. For example, using an etchant resulting from mixing 
H.sub.2 O of 63.3 wt %, KOH of 23.4 wt % and isopropanol of 13.3 wt % 
together, a (100) face can be selectively left, as a result of which the 
seed crystal covered with the (100) face can be selectively left. 
Also, a (111) face can be selectively left by etching in a gas phase using 
hydrazine (N.sub.2 H.sub.4). Specifically, the (111) face can be left by 
dry etching using CIF.sub.3 and N.sub.2 H.sub.4 as an etching gas. 
Further, as a method of applying the energy in the above-mentioned 
structure, one or plural kinds of methods selected from a heating method, 
a laser beam irradiation method and an intense light beam irradiation 
method can be used simultaneously or gradually. For example, a laser beam 
can be irradiated while heating, a laser beam can be irradiated after 
heating, heating and the irradiation of a laser beam can be alternately 
conducted, or heating can be conducted after the irradiation of a laser 
beam. Also, the laser beam may be replaced by an intense light beam. 
In the case where the silicon film is used as a semiconductor film, and an 
energy is applied to the film to crystallize the silicon film, it is 
useful to use a metal element that promotes the crystallization of 
silicon. For example, when an amorphous silicon film formed by the plasma 
CVD technique or the low pressure thermal CVD technique is to be 
crystallized by heating, a heat treatment at a temperature of 600.degree. 
C. or higher for 10 hours or longer is required. However, in the case of 
using a metal element that promotes the crystallization of silicon, the 
effect equal to or more than that of the above-mentioned heat treatment 
can be obtained by a heat treatment at 550.degree. C. for 4 hours. 
Nickel is the highest in its effect and useful as the metal element that 
promotes the crystallization of silicon. Also, one kind of plural kinds of 
elements selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au can be 
used. In particular, Fe, Pd, Pt, Cu and Au can obtain the better effect 
next to Ni. 
A monocrystal-like region or a substantially monocrystal-like region can be 
formed in a predetermined region by conducting a crystal growth from the 
seed crystal. The monocrystal-like region or the substantially 
monocrystal-like region is defined as a region that satisfies conditions 
stated below. 
No grain boundary substantially exists in the region. 
A hydrogen or halogen element that neutralizes a point defect is contained 
at a density of 0.001 to 1 atm % in the region. 
Carbon and nitrogen atoms are contained at a density of 1.times.10.sup.16 
to 5.times.10.sup.18 atm cm-.sup.3 in the region. 
Oxygen atoms are contained at a density of 1.times.10.sup.17 to 
5.times.10.sup.19 atm cm-.sup.3 in the region. 
According to another aspect of the present invention, there is provided a 
method of manufacturing a semiconductor, comprising the steps of: 
forming a first silicon film on a substrate having an insulating surface; 
bringing said first silicon film in contact with a metal element that 
promotes the crystallization of silicon and holding said first silicon 
film; 
applying an energy to said first silicon film to crystallize said first 
silicon film; 
patterning said first silicon film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal 
orientation in said seed crystal; 
covering said seed crystal to form a second silicon film; 
bringing said first silicon film in contact with a metal element that 
promotes the crystallization of silicon and holding said first silicon 
film; 
applying an energy to said second silicon film to conduct a crystal growth 
from said seed crystal in said second silicon film. 
According to still another aspect of the present invention, there is 
provided a method of manufacturing a semiconductor, comprising the steps 
of: 
forming a first silicon film on a substrate having an insulating surface; 
applying an energy to said first silicon film to crystallize said first 
silicon film; 
patterning said first silicon film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal 
orientation in said seed crystal; 
covering said seed crystal to form a second silicon film; 
applying an energy to said first silicon film to conduct a crystal growth 
from said seed crystal in said first silicon film; and 
conducting a patterning including at least a removal of the region in which 
said seed crystal is formed to form an active layer of the semiconductor 
device. 
The above-mentioned structure is characterized in that the region of the 
active layer thus obtained comprises a monocrystal-like region or a 
substantially monocrystal-like region. This region is defined as a region 
in which no grain boundary substantially exists, a hydrogen or halogen 
element which neutralizes a point defect is contained at a density of 
0.001 to 1 atm %, carbon and nitrogen atoms are contained at a density of 
1.times.10.sup.16 to 5.times.10.sup.18 atm cm-.sup.3, and oxygen atoms are 
contained at a density of 1.times.10.sup.17 to 5.times.10.sup.19 atm 
cm-.sup.3. 
According to still another aspect of the present invention, there is 
provided a method of manufacturing a semiconductor, comprising the steps 
of: 
forming a first silicon film on a substrate having an insulating surface; 
applying an energy to said first silicon film to crystallize said first 
silicon film; 
patterning said first silicon film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal 
orientation in said seed crystal; 
covering said seed crystal to form a second silicon film; 
conducting a patterning to form said second silicon film in a rectangular 
shape; 
applying an energy to said second silicon film to conduct a crystal growth 
from said seed crystal in said second silicon film; and 
conducting a patterning including at least a removal of the region in which 
said seed crystal is formed with respect to said second silicon film to 
form an active layer of the semiconductor device; 
wherein said seed crystal is positioned at a corner of said second silicon 
film which is formed in the rectangular shape. 
A specified example using the above-mentioned structure is shown in FIG. 3. 
In FIG. 3, a seed crystal 303 is positioned at a corner portion 304 of an 
amorphous silicon film 302 which is formed in a rectangular shape, and a 
laser beam which has been processed into a beam linearly is irradiated 
onto the amorphous silicon film 302 from the corner while being scanned 
thereon to thereby crystallize the amorphous silicon film 302. 
FIG. 3 shows an example in which the silicon film 302 (amorphous silicon 
film) is patterned in a quadrangle. However, it may be of a square or a 
rectangle. 
According to yet still another aspect of the present invention, there is 
provided a method of manufacturing a semiconductor, comprising the steps 
of: 
forming a first silicon film on a substrate having an insulating surface; 
applying an energy to said first silicon film to crystallize said first 
silicon film; 
patterning said first silicon film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal 
orientation in said seed crystal; 
covering said seed crystal to form a second silicon film; 
conducting a patterning to form said second silicon film in a polygonal 
shape; 
applying an energy to said second silicon film to conduct a crystal growth 
from said seed crystal in said second silicon film; and 
conducting a patterning including at least a removal of the region in which 
said seed crystal is formed with respect to said second silicon film to 
form an active layer of the semiconductor device; 
wherein said seed crystal is positioned at a corner of said second silicon 
film which is formed in the polygonal shape. 
A specified example using the above-mentioned structure is shown in FIG. 4. 
In FIG. 4, a seed crystal 404 is positioned at a corner portion 403 of an 
amorphous silicon film 401 which is patterned in a pentagon of the home 
base type, and a laser beam which has been processed into a beam linearly 
is irradiated onto the amorphous silicon film 401 from the corner while 
being scanned thereon to thereby crystallize the amorphous silicon film 
401. 
FIG. 4 shows an example in which the silicon film is patterned in a 
pentagon. However, it may be of a polygon having more corners. It should 
be noted that as the number of corners is increased, the angle of a corner 
is necessarily increased more, to thereby reduce such an effect that 
crystallization progresses from the corner. 
According to yet still another aspect of the present invention, a method of 
manufacturing a semiconductor, comprising the steps of: 
forming a first silicon film on a substrate having an insulating surface; 
applying an energy to said first silicon film to crystallize said first 
silicon film; 
patterning said first silicon film to form a region that forms a seed 
crystal; 
etching said seed crystal to selectively leave a predetermined crystal face 
in said seed crystal; 
covering said seed crystal to form a second silicon film; 
applying an energy to said second silicon film to conduct a crystal growth 
from said seed crystal in said second silicon film; and 
patterning said second silicon film to remove at least a portion where said 
seed crystal exists; 
wherein said second silicon film after having been patterned contains 
therein a hydrogen of 0.001 to 1 atm % and a metal element that promotes 
the crystallization of silicon with a density of 1.times.10.sup.16 to 
1.times.10.sup.19 atm cm-.sup.3. 
In the above-mentioned structure, a silicon film which is formed typically 
through the plasma CVD technique or the low pressure thermal CVD technique 
is used for the first and second silicon films. 
The reason why the predetermined crystal surface is selectively left is to 
conduct the crystal growth so as to produce crystal more approximating 
monocrystal. Leaving the predetermined crystal surface may be achieved by 
using etching means having a selectivity with respect to the predetermined 
crystal surface. For example, using an etchant resulting from mixing 
H.sub.2 O of 63.3 wt %, KOH of 23.4 wt % and isopropanol of 13.3 wt % 
together, a (100) face can be selectively left, as a result of which the 
seed crystal covered with the (100) face can be selectively left. This is 
because the etching rate of the above-mentioned etchant with respect to 
the (100) face is lower than that of other crystal faces. 
Also, a (111) face can be selectively left by etching in a gas phase using 
hydrazine (N.sub.2 H.sub.4). Specifically, the (111) face can be left by 
dry etching using CIF.sub.3 and N.sub.2 H.sub.4 as an etching gas. This is 
also because the etching rate of hydrazine with respect to the (100) face 
is lower than that of other crystal faces. 
Further, as a method of applying the energy in the above-mentioned 
structure, one or plural kinds of methods selected from a heating method, 
a laser beam irradiation method and an intense light beam irradiation 
method can be used simultaneously or gradually. For example, a laser beam 
can be irradiated while heating, a laser beam can be irradiated after 
heating, heating and the irradiation of a laser beam can be alternately 
conducted, or heating can be conducted after the irradiation of a laser 
beam. Also, the laser beam may be replaced by an intense light beam. 
In the case where the silicon film is used as a semiconductor film, and an 
energy is applied to the film to crystallize the silicon film, it is 
useful to use a metal element that promotes the crystallization of 
silicon. For example, when an amorphous silicon film formed by the plasma 
CVD technique or the low pressure thermal CVD technique is to be 
crystallized by heating, a heat treatment at a temperature of 600.degree. 
C. or higher for 10 hours or longer is required. However, in the case of 
using a metal element that promotes the crystallization of silicon, the 
effect equal to or more than that of the above-mentioned heat treatment 
can be obtained by a heat treatment at 550.degree. C. for 4 hours. 
Nickel is the highest in its effect and useful as the metal element that 
promotes the crystallization of silicon. Also, one or plural kinds of 
elements selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au can be 
used. In particular, Fe, Pd, Pt, Cu and Au can obtain the better effect 
next to Ni. 
A monocrystal-like region or a substantially monocrystal-like region can be 
formed in a predetermined region by conducting a crystal growth from the 
seed crystal. The monocrystal-like region or the substantially 
monocrystal-like region is defined as a region that satisfies conditions 
stated below. 
No grain boundary substantially exists in the region. 
A hydrogen or halogen element that neutralizes a point defect is contained 
at a density of 0.001 to 1 atm % in the region. 
Carbon and nitrogen atoms are contained at a density of 1.times.10.sup.16 
to 5.times.10.sup.18 atm cm-.sup.3 in the region. 
Oxygen atoms are contained at a density of 1.times.10.sup.17 to 
5.times.10.sup.19 atm cm-.sup.3 in the region. 
Also, with the removal of the region where a seed crystal exists, the 
density of the metal element in the monocrystal-like region or the 
substantially monocrystal-like region can be set to 1.times.10.sup.16 to 
1.times.10.sup.19 atm cm-.sup.3, preferably 1.times.10.sup.16 to 
5.times.10.sup.18 atm cm-.sup.3. 
The monocrystal-like region or the substantially monocrystal-like region is 
selectively formed, and thereafter an amorphous silicon film is formed 
with covering the seed crystal. Further, an energy is applied to the film 
by heating or irradiating a laser beam so that a crystal growth can 
progress from the seed crystal. Then, the monocrystal-like region or the 
substantially monocrystal-like region can be formed in the periphery of 
the seed crystal. 
The monocrystal-like region or the substantially monocrystal-like region 
can be formed into a desired region by selecting a region where the seed 
crystal is formed. Hence, the thin-film semiconductor device formed using 
that region can be formed into the desired region. 
In other words, a device equal to the device using the monocrystal silicon 
can be formed in a desired region. Also, with the use of the operation of 
a metal element that promotes the crystallization of silicon or the 
irradiation of a laser beam or an intense light beam, a glass substrate 
weak in heating can be used. 
A plurality of semiconductor regions obtained by patterning one 
monocrystal-like region or substantially monocrystal-like region commonly 
provide the same crystal axis and rotating angle around the crystal axis, 
respectively. The "crystal axis" called in this example defines a crystal 
axis 901 which is directed perpendicularly to a plane 903 in the 
monocrystal-like region or the substantially monocrystal-like region in 
FIG. 9. 
The orientation of the crystal axis can be made different depending upon a 
method of forming a starting film directed to the crystal axis and a 
crystallizing method. Specifically, a value such as a &lt;111&gt; axial 
orientation or a &lt;100&gt; axial orientation can be taken. 
The "rotating angle around the crystal axis" defines an angle indicated by 
reference numeral 902 in FIG. 9. This angle is of a relative angle which 
is measured with a reference of an arbitrary orientation. 
In the same monocrystal-like region or substantially monocrystal-like 
region, the crystal axes and the rotating angles therearound are identical 
or substantially identical to each other. 
Here, that the crystal axes are identical or substantially identical to 
each other is defined as that its deviated angle is in a range of 
.+-.10.degree.. Also, that the rotating angles are identical or 
substantially identical to each other is defined as that its deviated 
angle is in a range of .+-.10.degree.. 
Therefore, when the same monocrystal-like region or substantially 
monocrystal-like region is patterned to form a plurality of semiconductor 
regions, and a plurality of thin-film transistors are formed using those 
regions, the crystal axes of those active layers are identical to each 
other. Similarly, the angles around the crystal axes are identical to each 
other. 
Then, utilizing the above fact, plural pairs of thin-film transistors using 
the monocrystal-like region or substantially monocrystal-like region which 
commonly provide the same crystal axes and angles therearound can be 
formed as one group. For example, a CMOS circuit or an invertor circuit 
which are constituted by the combination of a p-channel type thin-film 
transistor with an n-channel type thin-film transistor can be comprised of 
a monocrystal-like region or substantially monocrystal-like region which 
commonly provide the same crystal axes and angles therearound.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, a description will be given in more detail of embodiments of the 
present invention with reference to the accompanying drawings. 
(First Embodiment) 
In a first embodiment, a crystalline silicon film is first formed on a 
glass substrate, and the crystalline silicon film is subjected to a 
patterning, to thereby form a region that forms a seed crystal. Then, an 
amorphous silicon film is formed thereon and then subjected to a heat 
treatment, to thereby conduct a crystal growth with a seed of the seed 
crystal to form a monocrystal-like region or a substantially 
monocrystal-like region. 
Hereinafter, a process of manufacturing a crystalline silicon film in 
accordance with this embodiment will be described with reference to FIGS. 
1A to 1E. First, a silicon oxide film 102 that forms an under film is 
formed at a thickness of 3000 .ANG. on a glass substrate 101 through the 
plasma CVD technique or the sputtering technique. The silicon oxide film 
102 functions as a barrier film for preventing a moving ion from entering 
a semiconductor film side from the glass substrate 101 or an impurity from 
being diffused in the semiconductor side. 
Thereafter, an amorphous silicon film 103 having a thickness of 1000 .ANG. 
is formed thereon through the plasma CVD technique or the low pressure 
thermal CVD technique. Furthermore, a nickel film 104 is formed on the 
surface of the amorphous silicon film 103 through the vapor deposition 
technique or the sputtering technique. The thickness of nickel is set to 
200 .ANG.. 
After the formation of the nickel film 104, it is subjected to a heat 
treatment at 300.degree. to 500.degree. C., in this example, 450.degree. 
C., for one hour, to form a nickel silicide layer on an interface between 
the nickel film 104 and the amorphous silicon film 103. Since the heat 
treatment is made for forming the nickel silicide layer, the heat 
treatment is conducted at a temperature of 500.degree. C. or less where 
the amorphous silicon film 103 is not crystallized for about 1 to 2 hours 
(FIG. 1A). 
Also, the irradiation of a laser beam may be substituted for the heat 
treatment to form the nickel silicide layer. Alternatively, the heat 
treatment and the irradiation of the laser beam may be used together to 
form the nickel silicide layer. 
After the nickel silicide layer has been formed on the interface between 
the nickel film 104 and the amorphous silicon film 103, a heat treatment 
is conducted for crystallizing the amorphous silicon film 103. This heat 
treatment is conducted under the conditions of 550.degree. C. and 4 hours. 
The upper limit of the conditions for the heat treatment is determined 
depending on a heat-resistant temperature of the glass substrate. It 
should be noted that the crystallization is enabled even at a temperature 
of about 500.degree. C., but since it takes 10 hours or more for the 
treatment, the productivity is lowered. 
Also, the irradiation of a laser beam or an intense light beam may be 
substituted for the heat treatment to crystallize the amorphous silicon 
film 103. It is more effective that the irradiation of a laser beam or an 
intense light beam and heating are conducted together. Further, it is also 
effective to conduct heating after the irradiation of a laser beam. 
Similarly, it is effective to alternately repeat the irradiation of a 
laser beam and heating. 
The crystallization due to the above-mentioned heat process is conducted 
while the nickel silicide component in the nickel silicide layer is 
changed into a crystal nucleus. In case of applying such a method, the 
density of nickel in the crystalline silicon film obtained is very high 
(it becomes about 10.sup.20 atms cm-.sup.3 or more), and therefore it 
cannot be used for a semiconductor device without any change. However, its 
crystalline property can be extremely enhanced. 
After the crystallization due to the heat treatment has been finished, an 
etching is conducted using an FPM to selectively remove the nickel film 
104 and the nickel silicide. The FPM is hydrofluoric acid to which 
over-water is added and has a function of selectively removing impurities 
contained in silicon. In this case, the nickel film 104 and the nickel 
silicide layer can be selectively removed. Also, the nickel component in 
the crystalline silicon film obtained can be removed. 
In the above-mentioned manner, a crystalline silicon film 105 is obtained. 
The crystalline silicon film 105 is excellent in its crystalline property, 
but since the density of nickel in the film 105 is high, it cannot be used 
for a semiconductor device without any change (FIG. 1B). 
Subsequently, a patterning is so conducted as to form island-like regions 
that form seeds 106 and 107 (hereinafter referred to as "seed crystal") of 
crystal growth. The island-like regions are set to a size of 0.1 to 
several tens .mu.m square. It is necessary that the size of the patterning 
is set to 0.1 to 5 .mu.m square, preferably 0.1 to 2 .mu.m square. This is 
because the monocrystalline property of the seed crystal is obtained. In 
this state, an etching is further conducted by the FPM (an etchant 
obtained by adding over-water to hydrofluoric acid), to remove the nickel 
component exposed on the surface of the seed crystal. 
Then, a laser beam is irradiated onto those island-like regions to thereby 
enhance the crystalline property of those island-like regions. In this 
situation, since those island-like regions are of fine regions, they can 
be changed into monocrystal-like regions or substantially monocrystal-like 
regions. In this manner, the seed crystals 106 and 107 can be obtained 
(FIG. 1C). 
In irradiating the laser beam, it is important to heat the regions to be 
irradiated at a temperature within a range of 450.degree. C. to the strain 
point of a glass. As the temperature of the glass is higher, the resultant 
effect is increased. However, it is necessary to set the temperature to 
the strain point of the glass substrate 101 to be used, or lower from the 
viewpoint of the heat resistance of the glass substrate. It should be 
noted that, in case of using a heat-resistant material such as a quartz 
substrate or a semiconductor substrate as a substrate, it may be heated at 
a high temperature of about 800.degree. to 1000.degree. C. Also, the heat 
treatment may be conducted by a method using a heater or a method of 
irradiating an infrared ray or other intense light beams. 
Subsequently, a chemical etching is conducted in such a manner that a 
crystal face having a specified orientation is left in the seed crystals 
106 and 107. For example, using an etchant resulting from mixing H.sub.2 O 
of 63.3 wt %, KOH of 23.4 wt % and isopropanol of 13.3 wt% together, a 
(100) face can be selectively left, as a result of which the seed crystals 
covered with the (100) face can be selectively left. 
Also, a (111) face can be selectively left by conducting an etching in a 
gas phase using hydrazine (N.sub.2 H.sub.4). Specifically, the (111) face 
can be left by dry etching using CIF.sub.3 and N.sub.2 H.sub.4 as an 
etching gas. That is, hydrazine has the highest etching rate at the (100) 
face. Compared with the (100) face, the etching rate at the (111) face is 
extremely low. The etching rates at other crystal faces are also higher 
than the etching rate at the (111) face. Hence, the (111) faces can be 
selectively left by etching using hydrazine. 
The seed crystals 106 and 107 thus obtained have the nickel component 
removed as much as possible (however, nickel exists to the density level 
that adversely affects the semiconductor device) and are constituted by 
the monocrystal-like region or the substantially monocrystal-like region. 
As a result, in the crystal growth at a post-stage, it can function as a 
nucleus of crystal growth. 
Then, an amorphous silicon film 108 having a thickness of 300 .ANG. is 
formed entirely over the seed crystals 106 and 107. The formation of the 
amorphous silicon film 108 is performed through the plasma CVD technique 
or the low pressure thermal CVD technique. In particular, from the 
viewpoint of a step coverage, it is preferable to use the low pressure 
thermal CVD technique. Thereafter, a heat treatment is conducted to 
thereby crystallize the amorphous silicon film 108. In this example, a 
heat treatment at 600.degree. C. for 8 hours is conducted to thereby 
crystallize the amorphous silicon film 108. 
In this process, the crystal growth progresses with nuclei of the seed 
crystals 106 and 107. In this way, monocrystal-like regions or 
substantially monocrystal-like regions 108 and 109 are formed. In this 
crystal growth, the crystal face from which the seed crystals 106 and 107 
are exposed grows up. For example, when the (100) face is selectively left 
in the seed crystals 106 and 107, the upper surfaces of the regions 110 
and 109 have the (100) faces. 
The crystal growth progresses toward the periphery of the seed crystals 106 
and 107. Then, a grain boundary 110 is formed at a portion where the 
crystal growth from the seed crystal 106 and the crystal growth from the 
seed crystal 107 collide with each other. 
FIG. 2 shows a state where the crystal growth is finished, taken from the 
top. Shown in FIG. 2 is a state in which the crystal growth progresses 
from the two seed crystals 106 and 107. The cross-section taken along a 
line A A' of FIG. 2 corresponds to a state shown in FIG. 1E. 
The monocrystal-like regions or the substantially monocrystal-like regions 
as indicated by reference numerals 109 or 120 in FIGS. 1A to 1E and 2 can 
obtain a size of several tens to several hundred .mu.m or more. 
The important matter is that a place at which the monocrystal-like region 
or the substantially monocrystal-like region is formed can be arbitrarily 
controlled by controlling a position at which the seed crystal is formed. 
Finally, the portions of the seed crystals 106 and 107 are removed by 
etching. In this way, a process of forming the monocrystal-like region or 
the substantially monocrystal-like region on the glass substrate is 
finished. Thereafter, a variety of thin-film semiconductor devices may be 
formed in accordance with known processes. 
In case of applying the structure shown in this embodiment, the 
monocrystal-like region or the substantially monocrystal-like region can 
be formed at an arbitrary place on the glass substrate. 
The density of nickel elements in the monocrystal-like region or the 
substantially monocrystal-like region from which the seed crystal region 
has been removed (after the patterning has been conducted) can be set to 
1.times.10.sup.16 to 1.times.10.sup.19 atms cm-.sup.3, more preferably 
1.times.10.sup.16 to 5.times.10.sup.18 atms cm-.sup.3. Then, the use of 
this region realizes the thin-film semiconductor device which is little 
influenced by nickel. 
(Second Embodiment) 
A second embodiment is characterized, as shown in FIG. 3, in that a linear 
laser beam is irradiated onto the amorphous silicon film 302 formed in the 
rectangular shape, starting from a corner portion 304 of the amorphous 
silicon film 302 while the linear laser beam is scanned thereon, to 
thereby conduct a crystal growth in a direction indicated by an arrow 305. 
In this example, the corner portion 304 of the amorphous silicon film 302 
which has been processed in the rectangular shape is formed with a seed 
crystal 303. In order to realize such a state, the seed crystal 303 is 
first formed on the glass substrate 300 by the method described with 
reference to the first embodiment, and the amorphous silicon film 302 is 
further formed thereon. Then, the amorphous silicon film 302 is so 
patterned as to be formed in the rectangular shape, to thereby obtain the 
state shown in FIG. 3. 
When a laser beam is irradiated onto the amorphous silicon film 302 in the 
state shown in FIG. 3, the crystal growth progresses toward a direction 
along which its area is gradually increased starting from the seed crystal 
303. As a result, the amorphous silicon film 302 of the rectangular shape 
can be changed into the monocrystal-like region or the substantially 
monocrystal-like region. 
In FIG. 3, only one amorphous silicon film 302 is shown for the 
simplification of description, but the amorphous silicon films 302 of the 
required number may be provided. However, it is important to make their 
directions identical to each other. 
After obtaining the monocrystal-like region or the substantially 
monocrystal-like region, a patterning is so conducted as to form an active 
layer of a thin-film transistor. In this situation, it is important to 
remove the portion of the seed crystal 303. For example, the size of the 
amorphous silicon film which has been patterned in the rectangular shape 
and is indicated by reference numeral 302 is set to several tens to 
several hundred % of the active layer of the thin-film transistor as 
required, and after the crystallization has been finished, it is patterned 
into an active layer. 
(Third Embodiment) 
A third embodiment is characterized in that a linear laser beam is 
irradiated onto an amorphous silicon film 401 which has been processed in 
the shape shown in FIG. 4, starting from a corner portion 403 of the 
amorphous silicon film 401 while the linear laser beam is scanned thereon, 
whereby the amorphous silicon film 401 is changed into a monocrystal-like 
region or a substantially monocrystal-like region. In the state shown in 
FIG. 4, a seed crystal 404 is formed on the portion 403 which is a 
starting point from which the crystal growth starts. The method of forming 
the seed crystal 404 may be the one described with reference to the first 
embodiment. 
As the laser beam is irradiated onto the amorphous silicon film 401 in the 
scanning manner in the state shown in FIG. 4, the crystallization 
progresses toward a direction along which its area is gradually increased. 
As a result, the entire amorphous silicon film 401 can be finally changed 
into the monocrystal-like region or the substantially monocrystal-like 
region. 
After obtaining the monocrystal-like region or the substantially 
monocrystal-like region, a patterning is so conducted, for example, as to 
form an active layer of the thin-film transistor. In this situation, it is 
important to remove the portion of the seed crystal 404. 
(Fourth Embodiment) 
A fourth embodiment shows an example of forming a circuit in which a 
p-channel type thin-film transistor and an n-channel type thin-film 
transistor are constituted into a complementary type with the application 
of the method described in the first embodiment. 
First, a state shown in FIG. 5A is obtained through the method described 
with reference to the first embodiment. The state shown in FIG. 5A is 
identical to that shown in FIG. 1E. After obtaining the state shown in 
FIG. 5A, a patterning is conducted to form active layers 501 and 502 of a 
thin-film transistor. In this patterning process, seed crystals 106 and 
107 and the region of a grain boundary 110 are removed. This is because 
nickel elements used in the crystallization process remain at a high 
density in the region of the seed crystals 106 and 107, and impurities are 
segregated in the grain boundary 110. 
The density of nickel elements inside of a monocrystal-like region or a 
substantially monocrystal-like region thus obtained is 5.times.10.sup.18 
atms cm-.sup.3 or less, and therefore there is no problem as to the 
existence of nickel atoms. 
In this embodiment, a region indicated by reference numeral 501 becomes an 
active layer of an n-channel type thin-film transistor. Also, a region 
indicated by reference numeral 502 becomes an active layer of a p-channel 
type thin-film transistor. Subsequently, a silicon oxide film 503 that 
functions as a gate insulating film is formed at a thickness of 1000 
.ANG.. Furthermore, an n-type microcrystal silicon film doped with a large 
amount of phosphorus is formed through the low pressure thermal CVD 
technique and then subjected to a patterning, to thereby form gate 
electrodes 504 and 505 (FIG. 5C). 
Further, in a state where the respective thin-film transistor regions are 
covered with a resist mask in that situation, phosphorus ions and boron 
ions are alternately implanted so that a source region 506, a drain region 
508 and a channel formation region 507 of an n-channel type thin-film 
transistor (TFT) are formed in the self-matching fashion. Also, a source 
region 511, a drain region 509 and a channel formation region 510 of a 
p-channel type thin-film transistor (TFT) are formed in the self-matching 
fashion (FIG. 5C). 
Sequentially, a silicon oxide film 512 having a thickness of 6000 .ANG. is 
formed as an interlayer insulating film through the plasma CVD technique. 
Furthermore, contact holes are so defined as to form source electrodes 513 
and 516 as well as drain electrodes 514 and 515 by double layer films 
consisting of a titan film and an aluminum film. In this example, the 
drain electrodes 514 and 515 are connected to each other to constitute a 
CMOS structure. In this way, a state in which the n-channel type thin-film 
transistor and the p-channel type thin-film transistor are constituted in 
the complemental type as shown in FIG. 5D is obtained. 
When the structure of this embodiment is applied, since the active layers 
of the respective thin-film transistors can be structured by the 
monocrystal-like region or the substantially monocrystal-like region, it 
can obtain the characteristic equal to that of a transistor constituted by 
use of a monocrystal silicon wafer. Then, an integrated circuit 
constituted by the transistor using monocrystal silicon can be structured. 
(Fifth Embodiment) 
A fifth embodiment is a modified example of the process shown in FIG. 1. 
This embodiment is characterized in that, in the process shown in FIG. 1D, 
nickel elements are held in contact with the entire surface of the 
amorphous silicon film 108, and thereafter it is subjected to a heat 
treatment, to thereby crystallize an amorphous silicon film 108. 
In order to conduct solid-phase crystallization using a metal catalyst for 
the promotion of crystallization, several methods are proposed. 
As one method thereof, in the case of a "physical formation" in which a 
coating of metal catalyst (Ni, Fe, Ru, Rh Pd, Os, Ir, Pt, Cu, Au, etc.) is 
formed through the sputtering technique, the electron beam vapor 
deposition technique, etc., even though a mean thickness of the metal 
coating is set to 5 to 200 .ANG., for example, 10 to 50 .ANG., the 
catalyst is liable to be formed on a surface to be formed in the form of 
an island. 
In other words, the metal catalyst becomes fine particles, a mean diameter 
of which is 50 to 200 .ANG., and is liable to be dispersed. Also, 
intervals between the respective fine particles are about 100 to 1000 
.ANG.. In other words, this causes a discontinuous layer to be formed and 
makes it hard to form a continuous film. 
The metal islands form a nucleus of crystallization, from which the crystal 
growth of the amorphous silicon film on the insulating layer is conducted 
through a heat treatment at 450.degree. to 600.degree. C. 
In the above-mentioned technique, a temperature under crystallization can 
be lowered by at least 50.degree. to 100.degree. C. in comparison with a 
temperature when the crystallization is conducted without any use of the 
above-mentioned catalyst. However, it has been found as a result of 
carefully observing the crystallized coating that a very large amount of 
amorphous components remain and form a metal region having a metal 
property. It is supposed that the metal nuclei have remained as they were. 
The metal region acts as a recombination center of electrons and holes in a 
semiconductor region which has been crystallized. The metal region has 
such a very adverse characteristic that, when a reverse bias voltage is 
applied across a semiconductor device, in particular, a semiconductor 
device having the p-i and n-i junctions, the metal region that almost 
always exists in the semiconductor region having the p-i and n-i junctions 
makes a leak current increase. 
For example, in the case of the structure of a TFT of the thin-film type 
having a channel length/channel width=8 .mu.m /8 .mu.m, an off-state 
current which should be naturally about 10-12 A is increased to 10.sup.-10 
to 10.sup.-6 A, that is 10.sup.2 to 10.sup.6 times as large as the former. 
In order to eliminate the above-mentioned drawback, this embodiment 
provides a "chemical formation" method as a method of forming a metal 
catalyst coating. 
In this method, a metal compound which has been diluted with a solution 
(water, isopropyl alcohol, etc.) at a density of 1 to 1000 ppm, typically 
10 to 100 ppm is used. In particular, an organometal compound is used. 
Hereinafter, various examples of metal compounds available to the chemical 
formation method will be described. 
(1) In case of using Ni as a catalyst element: 
At lease one kind of nickel compound selected from nickel bromide, nickel 
acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, 
nickel nitrate, nickel sulfate, nickel formate, nickel oxide, nickel 
hydroxide, nickel acetylacetonate, nickel 4-cyclohexyl butyrate, and 
nickel 2-ethyl hexanoic acid can be used. 
Also, Ni may be mixed with at least one selected from benzene, toluene 
xylene, carbon tetrachloride, chloroform, ether, trichloroethylene, and 
freon, all of which are a non-polar solvent. 
(2) In case of using Fe (iron) as a catalyst element: 
A material known as ion salt, for example, bromide (FeBr.sub.2 6H.sub.2 O), 
iron (II) bromide (FeBr.sub.3 6H.sub.2 O), iron (II) acetate (Fe(C.sub.2 
H.sub.3 O.sub.2).sub.3 .times.H.sub.2 O), iron (I) chloride (FeCl.sub.2 
4H.sub.2 O), iron (II) chloride (FeCl.sub.3 6H.sub.2 O), iron (II) 
fluoride (FeF.sub.3 3H.sub.2 O), iron (II) nitrate (Fe(NO.sub.3) 9H.sub.2 
O), iron (I) phosphorate (Fe.sub.3 (PO.sub.4).sub.2 8H.sub.2 O), and iron 
(II) phosphorate (FePO.sub.4 8H.sub.2 O) can be selectively used. 
(3) In case of using Co (cobalt) as a catalyst element: 
A cobalt compound is selected from a material known as a cobalt salt, for 
example, cobalt bromide (CoBr 6H.sub.2 O), cobalt acetate (Co(C.sub.2 
H.sub.3 O.sub.2).sub.2 4H.sub.2 O), cobalt chloride (CoCl.sub.2 6H.sub.2 
O), cobalt fluoride (CoF.sub.2 Xh.sub.2 O), and cobalt nitrate 
(Co(No.sub.3).sub.2 6H.sub.2 O), and can be use. 
(4) In case of using Ru (ruthenium) as a catalyst element: 
As a ruthenium compound, a material known as ruthenium salt, for example, 
ruthenium chloride (RuCl.sub.3 H.sub.2 O) can be used. 
(5) In case of using Rh (rhodium) as a catalyst element: 
As a rhodium compound, a material known as rhodium salt, for example, 
rhodium chloride (RhCl.sub.3 3H.sub.2 O) can be used. 
(6) In case of using Pd (palladium) as a catalyst element: 
As a palladium compound, a material known as palladium salt, for example, 
palladium chloride can be used. 
(7) In case of using Os (osmium) as a catalyst element: 
As an osmium compound, a material known as osmium salt, for example, osmium 
chloride (OsCl.sub.3) can be used. 
(8) In case of using Ir (iridium) as a catalyst element: 
As an iridium compound, a material known as iridium salt, for example, a 
material selected from iridium trichloride (IrCl.sub.3 3H.sub.2 O) and 
indium tetrachloride (IrCI.sub.4) can be used. 
(9) In case of using Pt (platinum) as a catalyst element: 
As a platinum compound, a material known as platinum salt, for example, 
platinum (II) chloride (PtCl.sub.4 5H.sub.2 O) can be used. 
(10) In case of using Cu (copper) as a catalyst element: 
As a copper compound, a material selected from copper (II) acetate 
(Cu(CH.sub.3 COO).sub.2), copper (II) chloride (CuCl.sub.2 2H.sub.2 O) and 
copper (II) nitrate (Cu(NO.sub.3).sub.2 3H.sub.2 O) can be used. 
(11) In case of using gold as a catalyst element: 
As a gold compound, a material selected from gold trichloride (AuCl.sub.3 
Xh.sub.2 O), gold nitride (AuHCl.sub.4 4H.sub.2 O) and sodium 
tetrachloroaurate (AuNaCl.sub.4 2H.sub.2 O) can be used. 
Each of the above materials can be sufficiently dispersed into a 
monomolecule in the solvent. 
The solvent droplets are dropped on a surface to be formed, to which a 
catalyst is to be added, rotated at a speed of 50 to 500 revolutions/min 
(RPM), and is spin-coated. As a result, the solvent can be spread over the 
entire surface. 
In this situation, in order to promote the uniform wetting property of the 
surface of the silicon semiconductor, if a silicon oxide film having a 
thickness of 5 to 100 .ANG. is formed on the surface of the silicon 
semiconductor, the solvent can be sufficiently prevented from existing in 
the form of points on the surface thereof by means of the surface tension 
of liquid. 
Also, when an interfacial active agent is added to liquid, a good uniform 
wetting state can be obtained even on the silicon semiconductor having no 
silicon oxide film. 
Those methods enable the metal catalyst to be dispersed into the 
semiconductor through the oxide film in the form of atoms, and in 
particular, they enable the metal catalyst to be dispersed to conduct 
crystallization without positively making the crystal nucleus 
(particle-shaped). Thus, the above methods are preferable. 
Also, an organometal compound is uniformly coated on the silicon 
semiconductor and then subjected to an ozone processing (ultraviolet rays 
(UV) in oxygen), to form a metal oxide film. The metal oxide film comes in 
a starting state of crystallization. As a result, because an organic 
substance is oxidized and can be gasified and removed as a carbon dioxide 
gas, a more uniform solid-phase growth can be made. 
Also, when the spin coating is conducted only at a low-speed rotation, the 
metal components in the solvent, which exists on the surface is liable to 
be supplied to the semiconductor film by an amount more than that as 
required for the solid-phase growth. For that reason, after the spin 
coating has been made at the low-speed rotation, a substrate is rotated at 
1000 to 10000 rpm, typically 2000 to 5000 rpm. Then, all the excessive 
organometal is shook off outwardly so as to be removed, and simultaneously 
the surface can be satisfactorily dried. Also, it is effective to fix the 
amount of the organometal existing on the surface. 
The chemical formation method as described above enables a continuous layer 
to be formed without making a nucleus due to the metal particles for 
crystallization on the surface of the semiconductor. 
The physical formation is liable to form an inhomogeneous layer whereas the 
chemical formation extremely readily forms a homogeneous-layer. 
Using the above-mentioned technical concept, when thermal crystallization 
is to be conducted at 450.degree. to 650.degree. C., the crystal growth 
can be extremely uniformly made over all the surface. 
As a result, even though a reverse bias voltage is applied across a 
semiconductor having the p-i and n-i junctions which has been formed using 
a semiconductor film which has been crystallized through that chemical 
formation method, its leak current can be restrained to a level of 
10-.sup.12 A at most of the semiconductor. 
In the physical formation method, there is a case where 90 to 100 per 100 
p-i junctions have a leak current of 10-.sup.10 to 10-.sup.5 A, and 50 to 
70 per 100 n-i junctions have a large leak current of 10-.sup.12 to 
10-.sup.6 A. 
On the other hand, in the chemical formation method, 5 to 20 per 100 p-i 
junctions have a leak current of 10-.sup.13 to 10-.sup.8 A, and 0 to 5 per 
100 n-i junctions have a leak current of 10-.sup.13 to 10-.sup.8 A. Thus, 
the characteristics are remarkably improved such that the off-state 
current is decreased, and a film causing a large leak current is reduced. 
Also, when a semiconductor film is formed on the insulating surface to form 
a TFT, even though the TFT is of the p-channel TFT (p-i-p) type or the 
n-channel TFT (n-i-n) type, the same remarkable excellent effects can be 
obtained. 
Furthermore, that off-state current allows the existing probability of the 
TFTs having a large leak current to be lowered by about 1 to 2 figures in 
comparison with the physical formation method. 
However, in order to form a thin-film integrated circuit by using this TFT, 
the existing probability of the TFTs having a large leak current is 
required to be 1/10.sup.3 to 1/10.sup.9. 
Also, after the thermal crystallization has been conducted with the 
addition of a catalyst metal through the above-mentioned chemical 
formation method, a laser beam of 248 mm or 308 mm is irradiated onto its 
surface with the intensity of 250 to 400 mJ/cm.sup.2. Then, a light 
absorption to a laser beam is large particularly in a region having a 
large amount of metal components in comparison with the silicon film which 
has been crystallized. In other words, this is because a region remaining 
in the form of the amorphous structure such as a metal becomes black 
optically. On the other hand, the crystal component is transparent. 
For that reason, the amorphous silicon component that slightly remains is 
selectively melted by the irradiation of a laser beam so that the metal 
components are diffused so as to be re-crystallized. The metal existing in 
that region can be diffused into an atom level unit. 
As a result, the existing probability of the metal region can be further 
decreased in the coating film thus formed, and an increase in the leak 
current, which is caused when the metal region comes to the recombination 
center of electrons and holes, is eliminated with the results that the 
off-state current at the n-i junction and the p-i junction of the TFT is 
10-.sup.13 to 10-.sup.12 A which is decreased by about 1 to 2 figures, and 
the number of TFTs having a large leak current can be reduced to 1 to 3 
per 10.sup.4 to 10.sup.8 TFTs. 
In this way, the reverse leak current, that is, I.sub.off is lowered by 2 
figures, and the existing probability of TFTs having a large leak current 
can be decreased by 2 figures at the maximum. It is assumed that a cause 
of allowing TFTs having a large leak current to still exist is that dusts 
are attached onto the surface of the semiconductor and organometal 
concentrates at that portion, and an improvement in those characteristics 
can be recognized because of an improvement in the performance of 
experimental devices. 
Also, in the physical formation method, as a result of attempting an 
experiment on the irradiation of a laser beam on a thermally crystallized 
film, there was a case where, because metal particles in the starting film 
become increased in size too large, even though the semiconductor is 
melted by the irradiation of a laser beam and recrystallized, an off-state 
current when a reverse bias is applied at the p-i and n-i junctions could 
not be reduced at all. 
In view of the above, the chemical formation of a continuous layer using a 
metal catalyst, the thermally crystallizing method accompanied by that 
formation and a semiconductor device formed by using such a method can 
readily obtain more excellent effects than the physical formation of a 
discontinuous layer using a metal catalyst and the thermal crystallizing 
method accompanied by that formation. 
One type of the chemical methods is a method of forming a metal compound, 
in particular, an organometal compound gas on a surface to be formed 
through the CVD technique instead fusing light. 
This method, as in the method using a liquid, has a remarkable effect in 
the reduction of an off-state current and the reduction of the existing 
probability of TFTs having a large leak current. 
Also, the physical formation method is liable to become nonuniform 
"anisotropic crystal growth" using a metal nucleus whereas the chemical 
formation method is comparatively easier to obtain a uniform crystal 
growth of "isotropic growth" using a uniform metal catalyst. 
The chemical method is of one type in which the crystal growth is made in a 
lateral direction with respect to the substrate surface, and of the other 
type in which the crystal grows vertically on the substrate surface, from 
the lower side toward the upper side of the semiconductor or from the 
upper side toward the lower side thereof, to thereby being capable of 
obtaining an excellent electric characteristic of the semiconductor. 
In order to hold the surface of the amorphous silicon film 108 in contact 
with nickel elements, as described above, a solvent containing a nickel 
element therein is coated on the surface of the amorphous silicon film 
108, and an excessive solvent is removed by a spinner. In this example, a 
nickel acetate solvent is used as a solvent. 
With the application of the structure described in this embodiment, a 
temperature required for crystallization can be lowered, and its period of 
time can be reduced. Specifically, in the structure shown in the first 
embodiment, a heat treatment for 8 hours or longer is required under the 
heat atmosphere of 600.degree. C. However, in the case of using nickel 
elements, the amorphous silicon film 108 can be crystallized under the 
condition where the heat treatment is conducted for 4 hours at 550.degree. 
C. 
However, in the case where the structure described in this embodiment is 
applied, the density of the metal element in the obtained monocrystal-like 
region or substantially monocrystal-like region becomes high. Hence, 
unless attention is given to the density of the introduced metal element, 
the characteristic of the obtained device is adversely affected by the 
metal element. 
Specifically, the density of the finally remaining metal elements must be 
set to be 1.times.10.sup.19 atms cm-.sup.3 or less. The adjustment of this 
density can be performed by adjusting the density of nickel in the 
solvent. It should be noted that the crystallization promoting action 
cannot be obtained when the density of the metal element that remains in 
the silicon film when crystallizing is 1.times.10.sup.16 atm cm.sub.-3 or 
less. Hence, the amount of metal elements to be introduced must be 
adjusted so that the metal elements exist in the silicon film at the 
density of 1.times.10.sup.16 to 1.times.10.sup.19 atm cm-.sup.3. 
(Sixth Embodiment) 
A sixth embodiment shows an example of obtaining a monocrystal-like region 
or substantially monocrystal-like region having a face orientation of its 
upper surface being the (100) face, using a seed crystal having a face 
orientation of a (100) face. 
FIG. 6 shows a state in which a monocrystal-like region or substantially 
monocrystal-like region is formed. In FIG. 6, reference numeral 62 denotes 
a seed crystal, and 61 is a monocrystal-like region or substantially 
monocrystal-like region which has been obtained by the crystal growth from 
the seed crystal 62. Also, a section taken along a line A--A' in FIG. 6A 
is shown in FIG. 6B. 
The monocrystal-like region or substantially monocrystal-like region 61 
shown in FIG. 6 is obtained as a substantially hexagonal region. 
A manufacturing process through which the state shown in FIG. 6 is obtained 
will be described. First, a silicon oxide film is formed on a glass 
substrate as an under layer (not shown), and an amorphous silicon film 
(not shown) is formed thereon. Then, the amorphous silicon film is 
crystallized through the same method as that in the first embodiment. In 
other words, nickel silicide which is a metal element that promotes the 
crystallization of silicon is formed on the amorphous silicon film, and 
then subjected to a heat treatment to crystallize the amorphous silicon 
film. Further, the amorphous silicon film is subjected to a patterning to 
form a base of the seed crystal 62. Thereafter, a laser beam is irradiated 
onto the amorphous silicon film while the silicon film being heated at 
450.degree. to 600.degree. C. (The upper limit of this temperature is 
determined by a strain point of the glass substrate.), to thereby obtain 
the seed crystal. 
Thereafter, the amorphous silicon film is formed on the seed crystal 62 and 
subjected to a predetermined heat treatment, thereby being capable of 
obtaining the monocrystal-like region or substantially monocrystal-like 
region 61. This state is shown in FIGS. 6A and 6B. 
Subsequently, portions of the seed crystal 62 and unnecessary portions are 
removed to thereby obtain active layers 64 and 66 which are formed by the 
monocrystal-like region or substantially monocrystal-like region. In this 
example, the seed crystal 62 contains a metal element (in this example, 
nickel) that promotes the crystallization of silicon as described in the 
first embodiment at a high density. Accordingly, by conducting the 
above-mentioned patterning, the characteristics of a manufactured device 
can be prevented from gradually fluctuating or being deteriorated by an 
influence of nickel. In this way, the state shown in FIG. 6C can be 
obtained. 
With the above process, as indicated by reference numerals 63 to 66 in FIG. 
6A, the active layers which are formed by the monocrystal-like region or 
substantially monocrystal-like region can be obtained. In the post-stage, 
a thin-film transistor may be manufactured by using those active layers 63 
to 66. 
(Seventh Embodiment) 
A seventh embodiment shows an example in which this invention described in 
this specification is applied to the active matrix liquid-crystal display 
unit having such a structure that even a peripheral circuit is integrated. 
FIG. 7 shows the structure of an outline of this embodiment. 
FIG. 7A shows peripheral circuits 702 and 703 formed on a glass substrate 
701 and a pixel region 704 disposed in the form of a matrix which is 
driven by the peripheral circuit. In order to constitute the 
liquid-crystal display unit, paired glass substrates on which opposing 
electrodes are formed is prepared and bonded to a substrate shown in FIG. 
7A so that liquid crystal is sealed therebetween to provide a 
liquid-crystal display unit. 
In the structure shown in FIG. 7A, the peripheral circuit is constituted by 
a thin-film transistor that includes the monocrystal-like region or 
substantially monocrystal-like region, and a thin-film transistor using an 
amorphous silicon film is disposed in a pixel region. The reason why an 
amorphous silicon film is used for the thin-film transistor disposed in 
the pixel region is that the practicability can be sufficiently obtained 
even by the thin-film transistor using an amorphous silicon film as a 
performance of the transistor for controlling the take-in and take-out of 
charges to/from the pixel electrode. In particular, in the case of a 
TN-type liquid crystal which is frequently used under existing 
circumstances, in the thin-film transistor which is formed by a silicon 
thin film having a crystalline property equal to that of monocrystal, the 
operating speed of a transistor is too high in comparison with the 
response speed of liquid crystal, resulting in a poor operating stability. 
Hence, such a structure that the peripheral circuit being capable of 
performing a high-speed operation is constituted by the thin-film 
transistor equivalent to the thin-film transistor using monocrystal 
silicon, and the thin-film transistor disposed in the pixel region is 
constituted by an amorphous silicon film is high in the practibility. 
A diagram partially enlarging the peripheral circuit 702 or 703 shown in 
FIG. 7A is shown in FIG. 7B. What is shown in FIG. 7B is an invertor 
circuit constituting a part of the peripheral circuit 702 or 703. 
Actually, a complicated integrated circuit is comprised of such an 
invertor and other required structures. It should be noted that the 
peripheral circuit 702 or 703 mentioned in this example defines a circuit 
including at least one selected from a circuit for driving a thin-film 
transistor and a shift register which are disposed in a pixel region, a 
variety of control circuits, a circuit that deals with a video signal, 
etc. 
In FIG. 7B, what is indicated by reference numeral 705 is a seed crystal, 
and the monocrystal-like region or substantially monocrystal-like region 
as indicated by reference numeral 708 is formed on the basis of the seed 
crystal 705. It should be noted that the monocrystal-like region or 
substantially monocrystal-like region 708 is patterned in a required 
pattern into a state where the seed crystal 705 is removed therefrom at a 
stage where the thin-film transistor is formed. 
FIG. 7B shows an example in which the n-channel thin-film transistor 717 
and the p-channel transistor 718 are constituted by using the 
monocrystal-like region or substantially monocrystal-like region 708, and 
an invertor circuit is constituted by those thin-film transistors. 
In the figure, there is shown an example of forming two thin-film 
transistors consisting of the n-channel thin-film transistor and the 
p-channel thin-film transistor in the monocrystal-like region or 
substantially monocrystal-like region 708. However, the thin-film 
transistors in the monocrystal-like region or substantially 
monocrystal-like region 708 may be formed in the required numbers or the 
possible numbers. 
Hereinafter, a process of manufacturing the structure shown in FIG. 7 will 
be described with reference to FIG. 8. What is shown in FIG. 8 is a 
process of manufacturing an invertor circuit formed in the peripheral 
region and a thin-film transistor which is connected to a pixel electrode 
formed in a pixel region. In this embodiment, the thin-film transistor 
forming the peripheral region is constituted by using the monocrystal-like 
region or substantially monocrystal-like region. Also, the thin-film 
transistor arranged in the pixel region is constituted by a thin-film 
transistor using an amorphous silicon film. 
First, a silicon oxide film 802 having a thickness of 3000 .ANG. is formed 
on a glass substrate 801. The glass substrate 801 constitutes one of a 
pair of glass substrates that form a liquid-crystal display unit. Then, a 
seed crystal 803 is formed through the method described with reference to 
the first embodiment. Moreover, an amorphous silicon film 804 having a 
thickness of 500 .ANG. is formed thereon (FIG. 8A). 
Subsequently, the monocrystal-like region or substantially monocrystal-like 
region is formed in the periphery of the seed crystal 803 by conducting a 
heat treatment and the irradiation of a laser beam together. In this 
example, a laser beam is irradiated onto only a region of the peripheral 
circuit by using an excimer laser beam of several cm.sup.2. In the 
irradiation of the laser beam, a heating temperature is set to 600.degree. 
C. Even though heating is conducted for a short period of time (the laser 
beam is irradiated for several minutes) at a temperature of 600.degree. 
C., since the amorphous silicon film is not crystallized, the amorphous 
silicon film 804 in the pixel region is not crystallized. This heating 
temperature is preferably as high as possible in a range where the glass 
substrate is not damaged. Also, in this example, a heating method in which 
infrared rays are irradiated is used in order to heat a silicon film for a 
short period of time. 
In this way, a region indicated by oblique lines in FIG. 8A can be changed 
into the monocrystal-like region or substantially monocrystal-like region. 
Also, in this state, a region except for that region indicated by the 
oblique lines is left in the state of the amorphous silicon film 804 as it 
is. 
Subsequently, active layers 806 and 807 of the thin-film transistor 
disposed in the peripheral circuit are formed by patterning. 
Simultaneously, an active layer 808 of the thin-film transistor connected 
to the pixel electrode is formed thereon. In this state, the active layers 
806 and 807 are constituted by the monocrystal-like region or 
substantially monocrystal-like region 805. Also, the active layer 808 is 
constituted by an amorphous silicon film 804. 
Then, a silicon oxide film 809 that functions as a gate insulating film is 
formed at a thickness of 1000 .ANG.. Thereafter, an aluminum film 
containing scandium of 0.2 wt % and having a thickness of 6000 .ANG. is 
formed through the sputtering technique or the electron beam vapor 
deposition technique and patterned to form gate electrodes 810, 811 and 
812. Further, anodic oxidation is conducted with those gate electrodes 810 
to 812 as anodes in an electrolyte, to thereby form an anodic oxidation 
film in the periphery of gate electrodes 810 to 812. Thus, a state shown 
in FIG. 8B is obtained. 
First, a region in which the n-channel thin-film transistor is to be formed 
is masked by a resist mask 800, and B (boron) ions which are impurities 
giving the p-type to silicon are implanted thereinto. The implantation of 
ions is conducted through the ion implantation technique or the plasma 
doping technique. Further, a region in which a p-channel thin-film 
transistor is to be formed is covered with a resist mask (not shown) and P 
ions are implanted thereinto. After those ion implantation processes have 
been completed, the activation of implanted ions and the annealing of 
damages accompanied by the implantation of ions are conducted by the 
irradiation of a laser beam (not shown). 
In the above-mentioned manner, as shown in FIG. 8C, a source region 813, a 
drain region 815 and a channel formation region 814 of the p-channel 
thin-film transistor (PTFT) are formed. Also, a source region 818, a drain 
region 816 and a channel formation region 817 of the n-channel thin-film 
transistor (NTFT) are formed. These two thin-film transistors are disposed 
in the periphery of the peripheral circuit and constituted by a region 
(C-Si) an active layer of which is the monocrystal-like region or 
substantially monocrystal-like region. 
Also, a source region 819, a drain region 821 and a channel formation 
region 820 of a thin-film transistor disposed in the pixel region are 
simultaneously formed. The thin-film transistor disposed in this pixel 
region is formed of an amorphous silicon film (a-Si). 
A process of forming those source and drain regions and the channel 
formation region by implanting impurity ions is conducted in the 
self-matching manner. 
After the source, the drain and the channel formation regions of each 
thin-film transistor have been formed, a silicon oxide film 822 having a 
thickness of 6000 .ANG. is formed as an interlayer insulating film through 
the plasma CVD technique. Furthermore, contact holes are formed so that a 
source electrode 823 of the p-channel thin-film transistor disposed in the 
peripheral circuit region, a drain electrode 824 common to the p-channel 
thin-film transistor and the n-channel thin-film transistor, and a source 
electrode 825 of the n-channel thin-film transistor are formed. 
Simultaneously, a source electrode 826 and a drain electrode 827 of the 
n-channel thin-film transistor disposed in the pixel region are formed. 
Those electrodes 823 to 827 are constituted by a three-layer structure 
where an aluminum film is interposed between two titan films. 
Furthermore, an ITO electrode 828 constituting a pixel electrode is formed. 
In this way, the thin-film transistor that constitutes a peripheral 
circuit formed by using the monocrystal-like region and a thin-film 
transistor using an amorphous silicon film and disposed in the pixel 
region can be simultaneously formed on the same glass substrate. In this 
manner, one substrate constituting the active matrix liquid-crystal 
display unit shown in FIG. 7 is completed. The structure thus obtained can 
be regarded as two thin-film transistors being formed as one pair by using 
a seed crystal 805. 
After the state shown in FIG. 8D has been obtained, a second interlayer 
insulating film is further formed, and an oriented film is formed on that 
film. Then, an opposing electrode is formed on each of opposing glass 
substrates, and an oriented film is formed on the opposing electrode, 
likewise. Thereafter, an orientation process is conducted, and the paired 
glass substrates thus manufactured is bonded to each other. Finally, 
liquid crystal is sealed between the paired glass substrates thus bonded, 
to thereby complete the active matrix liquid-crystal display unit panel. 
The liquid-crystal display unit described in this embodiment has such a 
structure that the peripheral circuits are integrated and therefore can be 
so structured as to be very compact and lightweighted. 
In this embodiment, as shown in FIG. 8, there is shown an example in which 
the paired thin-film transistors of the n-channel type and the p-channel 
type are formed by using the seed crystal 805 and constituted into the 
complemental type. However, this may be of a pair of thin-film transistors 
of the same channel type. Also, a pair of thin-film transistors of the 
n-channel type and the p-channel type may be formed and independently 
operated. 
(Eighth Embodiment) 
An eighth embodiment shows an example in which a pixel region 704 is of the 
passive type using no thin-film transistor, and only peripheral circuits 
702 and 703 are constituted by a monocrystal-like crystalline silicon film 
region or substantially monocrystal-like crystalline silicon film region 
shown in FIG. 7B, in the structure shown in FIG. 7A. 
Unless a complicated image information display is not conducted, there has 
been known that a known STN-type liquid-crystal display unit can be 
satisfactorily practically used. For example, the STN-type liquid-crystal 
display unit is used for a portable information device (a note-type word 
processor or personal computer) which is required to display only 
characters numerals and simple figures. However, under the existing 
circumstances, an IC attached externally is used for the peripheral 
circuit disposed in the periphery of the pixel region. 
In case of using the externally attached IC circuit, the thickness of a 
liquid-crystal panel is thickened, and its weight is also heavy. From this 
viewpoint, in the structure described in this embodiment, only the 
peripheral circuit is constituted by the circuit shown in FIG. 7B, to 
thereby integrate the liquid-crystal layer and the peripheral circuit on 
the glass substrate. With this structure, a liquid-crystal layer, an 
electrode and a wire applied to that liquid-crystal layer can be 
integrated between a pair of glass substrates, and further, the peripheral 
circuits indicated by reference numerals 702 and 703 in FIG. 7A can be 
integrated in the periphery of the liquid-crystal layer. Also, since the 
peripheral circuits 702 and 703 are integrated in a region a width of 
which is several mm, the entire structure can be made very compact. 
As was described above, according to the present invention, a region that 
forms a seed crystal is selectively formed, whereby the monocrystal-like 
crystalline silicon film region or substantially monocrystal-like 
crystalline silicon film region can be formed in an arbitrary region. 
Also, this region can be formed on the glass substrate. In case of using 
the present invention described in this specification, such a structure 
that the peripheral circuits of the active matrix liquid-crystal display 
unit are integrated on the glass substrate can be realized. In particular, 
the thin-film transistor constituting at least one of the peripheral 
circuits can provide the characteristics equivalent to that using a 
monocrystal silicon, that can contribute to the further weight-lightening 
and film-thinning of the thin-film transistor. The present invention 
described in this specification can be applied to a photoelectric 
conversion unit, a photosensor and a pressure sensor using a thin-film 
diode or a thin-film semiconductor, other than the thin-film transistor. 
The foregoing description of a preferred embodiment of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed, and modifications and variations are possible in light of the 
above teachings or may be acquired from practice of the invention. The 
embodiment was chosen and described in order to explain the principles of 
the invention and its practical application to enable one skilled in the 
art to utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. It is 
intended that the scope of the invention be defined by the claims appended 
hereto, and their equivalents.