Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-01-11
2002-05-21
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S532000
Reexamination Certificate
active
06392265
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Application No. 2000-3837, filed, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a method for fabricating the semiconductor device, more specifically to a semiconductor device comprising the capacitors formed of ferroelectric film.
An FRAM (Ferro-electric Random Access Memory) is a nonvolatile semiconductor memory using ferroelectric film as dielectrics of the capacitors. The FRAM is much noted for the high operation speed and low electric power consumption.
A structure of the capacitors of such FRAM will be explained with reference to FIG.
12
.
FIG. 12
is a conceptual view of the capacitors of the conventional semiconductor device.
As shown in
FIG. 12
, an IrO
2
film
130
and a Pt film
134
are formed the latter on the former, and the IrO
2
film
130
and the Pt film
134
form a lower electrode
136
.
A ferroelectric film
138
of a PbZr
x
Ti
1−x
O
3
(PZT) film or a SrBi
2
Ta
2
O
9
(SBT) film is formed on the lower electrode
136
.
An IrO
2
film
140
and a Pt film
144
are sequentially formed on the ferroelectric film
138
. The IrO
2
film
140
and the Pt film
144
form an upper electrode
146
.
The lower electrode
136
, the ferroelectric film
138
and the upper electrode
146
form a capacitor
148
.
However, in a case that, as shown in
FIG. 12
, the lower electrode
136
and the upper electrode
146
of the capacitor
148
are formed of Ir-family films, it is difficult to realize low-voltage operation and hydrogen deterioration resistance, which are required by the next generation devices.
As an electrode material which is able to realize improved low-voltage operation and hydrogen deterioration resistance, SRO (SrRuO
x
) film is noted. SRO film, which has perovskite structure, as have PZT and SBT, is not easily damaged in semiconductor device fabrication processes, and is expected to realize low-voltage operation. SRO film is a material of high resistance to hydrogen.
However, a capacitor formed of SRO film used as an electrode material Pb or Bi contained in the ferroelectric film tend to diffuse into the SRO film.
In view of this, a technique which can realize low-voltage operation and hydrogen deterioration resistance by using SRO film.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor device which can realize low-voltage operation and hydrogen deterioration resistance by using SRO film.
The above-described object is achieved by a semiconductor device comprising: a first electrode; a ferroelectric film formed on the first electrode; and a second electrode formed on the ferroelectric film, the first electrode or the second electrode comprising SrRuO
x
film with Pb and/or Bi added. Pb and Bi are added to the SRO film, whereby the diffusion of the Pb and Bi contained in the ferroelectric film into the SRO film are suppressed, which leads to an improvement of the capacitor ferroelectric properties. Thus, the semiconductor device can realize low-voltage operation and hydrogen deterioration resistance by using the SRO film.
REFERENCES:
patent: 6194228 (2001-02-01), Fujiki et al.
patent: 408340087 (1996-12-01), None
patent: 9-82906 (1997-03-01), None
patent: 9-191087 (1997-07-01), None
patent: 410182292 (1998-07-01), None
patent: 10-214947 (1998-08-01), None
patent: 2924753 (1999-05-01), None
Cross Jeffrey Scott
Kondo Kazuaki
Nguyen Cuong Q
Thomas Tom
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