Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-04-15
2003-04-22
Clark, Jasmine J B (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S308000, C257S310000, C257S313000, C257S900000, C257S027000, C257S027000
Reexamination Certificate
active
06552379
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, in particular, to a semiconductor device having a capacitor which does not leak and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, a film with a very good coverage, such as a silicon oxide film or a silicon nitride film made by means of a CVD (chemical vapor deposition) method, is used for the dielectric film of a capacitor. Therefore, a film of a uniform thickness can be formed even in the case that the lower electrode has a complex form. As for the structure of the complex lower electrode, a cylindrical structure, a thin structure, a structure where polysilicon is roughened, a trench structure, and the like, can be cited.
FIGS. 7
to
11
illustrate a process for a capacitor in a semiconductor device according to a prior art. First, a semiconductor substrate is provided below (see
FIG. 11
) and impurity regions formed in the semiconductor substrate and an insulating film
102
, which covers a channel region, are formed. A contact plug
103
which contacts the above impurity regions is provided in the above insulating film
102
. Next, a lower electrode layer
104
is formed so as to contact on the above contact plug
103
and insulating film
102
(FIG.
7
). This lower electrode layer can be formed of a metal film, such as platinum. Next, the lower electrode layer is patterned by using a resist pattern, or the like, as a mask so as to form a storage node (lower electrode)
104
a
(FIG.
8
).
Next, a dielectric film
105
is formed so as to cover the top surface and sidewalls of storage node
104
a
(FIG.
9
). After this, a conductive film
106
for an upper electrode is formed so as to contact and cover the top surface and side surfaces of dielectric film
105
(FIG.
10
). The semiconductor device shown in
FIG. 11
is formed according to a capacitor process as described above. In
FIG. 11
, capacitor contact plug
103
makes a conductive connection between storage node
104
a
and an impurity region
114
in the semiconductor substrate.
In addition, a bit line contact
108
makes a conductive connection between a bit line
107
and an impurity region
113
provided in the semiconductor substrate. In addition, a transfer gate
109
usually used as a word line is formed of a gate insulating film
110
on a channel region (not shown) in the semiconductor substrate, a barrier metal layer
109
b
contacting and located above the gate insulating film and a metal layer
109
a.
In recent years, new materials of a large dielectric constant, which allow a charge of a higher capacitance to be stored, have been developed as capacitor dielectric films. Therefore, application of these new materials to a semiconductor device has begun to be examined. As for these new materials, a BST ((Ba, Sr)TiO
3
: barium strontium titanium oxide) film or an ST (SrTiO
3
: strontium titanium oxide) film can be cited.
Though these materials have high dielectric constants and can implement a high capacitance, there is a problem wherein the coverage of the lower electrode is low. In particular, materials which cannot be formed by means of CVD and which can only be formed by means of spattering have very low coverage.
In the case that a material of low coverage is utilized, for example in the case that the lower electrode is in a plurality of convex forms separated from each other, the occurrence of a thin portion in the dielectric film at a corner portion, or the like, cannot be avoided. For example, in the case that a dielectric film with poor coverage or a dielectric film with a strong tendency to form crystals is formed as the capacitor dielectric film, a portion where the film is thin easily occurs in a portion of a corner of the storage node, such as portion B in FIG.
11
. When the film is too thin in such a portion of the dielectric film, it becomes a place where a leak of the charge stored in the capacitor occurs. In addition, when a dielectric film of a uniform thickness is provided in order to prevent the leak, the capacitance of the capacitor is lowered.
SUMMARY OF THE INVENTION
Purposes of the present invention are to provide a semiconductor device with a capacitor having a structure wherein there are no places that leak even in the case that a dielectric film of low coverage is thinly formed as well as to provide a process for the same.
A semiconductor device of the present invention is a semiconductor device provided with first and second capacitors adjoining each other, the respective lower electrode of which is electrically connected to impurity region in a semiconductor substrate and the respective upper electrode of which is electrically connected to an external wire. In this semiconductor device the first and the second capacitors, respectively, has lower electrode which contacts the top surface of an insulating layer formed on the semiconductor substrate and the top surface of plug wire running through the insulating layer, dielectric film which contacts the top surface of the lower electrode and which has peripheral sidewall surfaces that continue to the peripheral sidewall surfaces of the lower electrode, first upper electrode, which contacts the top surface of the dielectric film, and a second upper electrode, which contacts the top surface of the first upper electrode. The semiconductor device is further provided with a partition insulating film which contacts the top surface of the insulating film and which covers the sidewalls of the lower electrode and the dielectric film between the first and the second capacitors, wherein the second upper electrode contacts on the top surface of the partition insulating film.
In this structure, a dielectric film for a basic capacitor structure is formed of only a dielectric layer in a plane arranged on the lower electrode layer in a plane. Therefore, a dielectric film of poor coverage film or a dielectric film which has a strong tendency to form crystals does not cover lower electrodes of a complex form, such as those having corner portions. Therefore, no portions of the film become so thin so as to cause a leak. In addition, the dielectric film of the first and second capacitors can be formed at the same level. Therefore, individual capacitor can be patterned in a deposition layer which is broader in a plane. Therefore, a factor causing a large fluctuation of the film thickness in one capacitor can be eliminated as a result of this portions of an individual capacitor where the dielectric film is extremely thin do not occur and, thereby, a leak can be prevented. A dielectric material of a high dielectric constant, of which the coverage is poor, can be used in order to form this dielectric layer of a sufficient thinness and, thereby, a semiconductor device provided with a capacitor of high capacitance can be gained.
In the above described semiconductor device of the present invention, the partition insulating film can cover an area ranging from the lower end of the sidewalls of the first upper electrode to a predetermined level.
In this structure, it becomes easy to provide the second upper electrode over a plurality of capacitors without causing a leak. Therefore, it becomes possible to easily connect a plurality of capacitors through the second upper electrode.
In the semiconductor device of the present invention the partition insulating film can be made of an insulating film filled in to the gap between the first and the second capacitors.
In this structure individual capacitors can be separated from each other so as not to cause a leak in the individual capacitors.
In the above described semiconductor device of the present invention, the second upper electrode can be provided in a continuous form over the first and the second capacitors that are separated by the partition insulating film.
In this structure the upper electrodes of the plurality of capacitors can be easily connected. Accordingly, the freedom of arrangement of an external wire which is electr
Clark Jasmine J B
McDermott & Will & Emery
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