Dielectric device

DETAILED DESCRIPTION In view of the present need as described above, an object to the present invention is to provide a dielectric device having a high permittivity and sufficient dielectric characteristics.
According to the invention, a dielectric device comprises: a Si substrate; an oxide film formed on the Si substrate; and a Si-rich SiO.
sub.
2 nitride film formed on the oxide film and including SiO.
sub.
x regions and SiN.
sub.
x regions, the SiN.
sub.
x regions being formed by nitriding Si regions separated from a Si-rich SiO.
sub.
2 film.
Using more specific terms, the dielectric device of the invention includes the SiO.
sub.
2 film and the Si-rich SiO.
sub.
2 nitride layer that mainly consists of SiO.
sub.
2 regions and Si.
sub.
3 N.
sub.
4 regions.
The SiO.
sub.
2 film is to provide sufficient insulation (i.
e.
, dielectric breakdown) characteristics.
On the other hand, in the Si-rich SiO.
sub.
2 nitride film, while the SiO.
sub.
2 regions also work to provide the sufficient insulation characteristics, the Si.
sub.
3 N.
sub.
4 regions serve to increase the permittivity.
Since the Si.
sub.
3 N.
sub.
4 regions of the nitride film are a superior dielectric material though having insulation characteristics somewhat inferior to the SiO.
sub.
2 film, the SiO.
sub.
2 film used can be made thinner than the conventional dielectric device.
The capacitance of a capacitor is generally proportional to a relative permittivity of a dielectric material used therein.
In the invention, the partial occupation by the Si.
sub.
3 N.
sub.
4 regions, which have a relative permittivity larger than SiO.
sub.
2, makes it possible to provide a larger capacitance compared with a same-sized dielectric device having only a SiO.
sub.
2 film.
When compared with a dielectric device having the same capacitance and having only a SiO.
sub.
2 film, the area of the dielectric device can be made smaller by 10-20%.
It is noted that relative permittivities of SiO.
sub.
2 and Si.
sub.
3 N.
sub.
4 are 3.
9 and 7.
0, respectively.