Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-01-28
2004-05-18
Pham, Long (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S412000, C257S413000, C257S754000, C257S755000, C257S915000
Reexamination Certificate
active
06737716
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-022688, filed Jan. 29, 1999; No. 11-041343, filed Feb. 19, 1999; and No. 11-267207, filed Sep. 21, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a method of manufacturing the same, particularly, to improvement in performance of the gate insulating film.
With progress in miniaturization of a MOSFET, the gate electrode is required to have a lower resistance. Also, in a gate electrode using a polycrystalline silicon (polysilicon), the problem of depletion is not negligible nowadays. Therefore, it is of high importance to develop a gate structure consisting of a metal single layer. Concerning the gate insulating film, it is proposed to use a film made of a material having a high dielectric constant, e.g., TiO
2
, in place of SiO
2
for decreasing the equivalent oxide thickness of the gate insulating film.
FIGS. 14A
to
14
C show a conventional manufacturing process. In the first step, a TiO
2
film
502
is formed as a gate insulating film by a LP-CVD method in a thickness of about 10 nm on a silicon substrate
500
, as shown in FIG.
14
A. Used as the CVD gas is, for example, Ti(C
11
H
19
O
2
)
2
Cl
2
. Then, a TiN film
503
in a thickness of 10 to 20 nm is formed on the TiO
2
film
502
by a CVD method under a gaseous atmosphere of TiCl
4
and NH
3
as shown in FIG.
14
B. The TiN film
503
acts as a barrier metal layer serving to prevent diffusion of a gate electrode material into the gate insulating film or to control the work function. Further, a metal electrode
504
consisting of W, Al, Cu, etc. is formed by CVD on the TiN film
503
, as shown in FIG.
14
C.
However, the conventional method described above gives rise to a serious problem. Specifically, it is difficult to form the TiO
2
film
502
having oxygen supplied thereinto completely in the step shown in FIG.
14
A. Since the oxygen shortage functions as a donor in the TiO
2
film
502
, the insulating properties of the TiO
2
film are markedly deteriorated by a slight oxygen shortage. It should also be noted that the impurities contained in the CVD gas such as carbon and chlorine are left unremoved so as to cause the oxygen shortage. Further, the CVD film tends to become lower in density than the oxide film formed by thermal oxidation, as can be seen from CVD of a silicon oxide film. As a result, an oxygen shortage tends to be caused. Such being the situation, it is difficult to form a transistor having good characteristics and a high reliability.
On the other hand, the TiO
2
film
502
constituting the conventional gate insulating film leaves room for further improvement in the film structure.
FIGS. 15A and 15B
schematically show the film structure of the TiO
2
film
502
, wherein
FIG. 15A
is a cross sectional view, and
FIG. 15B
is a plan view.
In forming the TiO
2
film
502
in the step shown in
FIG. 14A
, a clear crystal grain boundary
512
is formed between adjacent crystal grains
511
of TiO
2
, as shown in
FIGS. 15A and 15B
. As a result, the electrical insulating properties of the TiO
2
film constituting the gate insulating film are markedly deteriorated, making it very difficult to prepare a MIS transistor having good characteristics and a high reliability.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor device in which insulating properties of the insulating film such as a gate insulating film are improved so as to improve the characteristics and reliability of the semiconductor device and a method of manufacturing the particular semiconductor device.
According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising:
forming a metal compound film directly or indirectly on a semiconductor substrate;
forming a metal-containing insulating film consisting of a metal oxide film or a metal silicate film by oxidizing the metal compound film; and
forming an electrode on the metal-containing insulating film.
In the first aspect of the present invention, the metal-containing insulating film may consist of a plurality of first insulating regions formed of grains containing a metal oxide of a metal element constituting the metal compound film and a second insulating region formed of an amorphous insulating material in a region except the first insulating regions.
According to a second aspect of the present invention, there is provided a semiconductor device, comprising:
a semiconductor substrate;
a metal-containing insulating film formed directly or indirectly on the semiconductor substrate, the metal-containing insulating film consisting of a plurality of first insulating regions formed of grains containing a metal oxide and a second insulating region formed of an amorphous insulating material in a region except the first insulating regions; and
an electrode formed on the metal-containing insulating film.
According to a third aspect of the present invention, there is provided a semiconductor device, comprising:
a first metal oxide film formed directly or indirectly on a semiconductor substrate;
a second metal oxide film formed on the first metal oxide film; and
a gate electrode formed on the second metal oxide film,
wherein, the decrease of the Gibbs free energy at the time when a metal constituting the gate electrode forms an oxide is larger than that at the time when a metal constituting the first metal oxide film forms an oxide, and the decrease of the Gibbs free energy at the time when a metal constituting the second metal oxide film forms an oxide is larger than or equal to that at the time when the metal constituting the gate electrode forms an oxide.
According to a fourth aspect of the present invention, there is provided a semiconductor device, comprising:
a semiconductor substrate having a trench;
a metal-containing insulating film consisting of a metal oxide film or a metal silicate film and formed along the inner surface of the trench, the metal-containing insulating film constituting a gate insulating film; and
a gate electrode formed on the metal-containing insulating film,
wherein a thickness A of the metal-containing insulating film in the center of the bottom portion, a thickness B of the metal-containing insulating film in the center of the side wall portion, and a thickness C of the metal-containing insulating film at the corner portion along a line joining the intersection between the bottom portion and the side wall portion of the trench and the intersection between the upper surface and the side wall surface of the metal-containing insulating film meet the relationship C
2
>(A
2
+B
2
).
According to a fifth aspect of the present invention, there is provided a semiconductor device, comprising:
a semiconductor substrate;
a gate insulating film formed on the semiconductor substrate;
a gate electrode formed on the gate insulating film;
a side wall insulating film formed along a side wall of the gate electrode;
a metal oxide film formed on the upper surface of the gate electrode;
diffusion layers formed within those portions of the semiconductor substrate which are positioned on both sides of the gate electrode;
source-drain regions formed on the diffusion layers and in contact with the side wall insulating film; and
silicide films formed on the source-drain regions, the upper surface of the silicide film being substantially flush with the upper surface of the metal oxide film.
In the fifth aspect of the present invention, the silicide film contains a noble metal forming a silicide at a temperature lower than the melting point of aluminum. The silicide film contains at least one of palladium, nickel, platinum and cobalt. Also, the gate electrode consists of aluminum, titanium, zirconium, hafnium, tantalum, niobium, vanadium or a nitride of any of these metals.
The present invention also provides
Matsuo Kouji
Nakamura Shin-ichi
Saito Tomohiro
Suguro Kyoichi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Pham Long
Rao Shrinivas H.
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