Capacitor device providing sufficient reliability

#The present application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-045550 filed on Feb. 26, 2007, with the Japanese Patent Office, the entire contents of which are incorporated herein by reference.

#1. Field of the Invention

#The disclosures herein relate to a capacitor device having a ferroelectric layer, a semiconductor device having such a capacitor device, and a method of manufacturing such a capacitor device.

#Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

#FIG. 1 is a drawing showing differences in the in-plane deformation of crystal depending on the presence/absence of Sc addition;

#FIG. 2 is a drawing showing the results of analysis performed by using XRF on a ferroelectric layer;

#A capacitor device according to an embodiment of the present invention includes a dielectric layer (ferroelectric layer), an upper electrode and lower electrode that are respectively placed on and beneath the dielectric layer, and a substrate for supporting the upper electrode, the lower electrode, and the dielectric layer.

#The crystal that constitutes the dielectric layer (ferroelectric layer) has a perovskite structure. The perovskite structure is represented by the general expression “ABO3”. The perovskite structure ideally has a unit lattice of a cubic system, with metal A situated at the vertexes of a cubical crystal, metal B situated at the body center, and oxide O situated at each face center of the cubical crystal surrounding the metal B. The above-noted structure is known to transform easily.

#The inventors of the present invention found that when Sc was added to barium strontium titanate having a perovskite structure to form a dielectric layer by use of a particular Sc-modified composition, the relative permittivity of the dielectric layer increased so as to be able to increase its volume density. In this case, further, the leak current in the dielectric layer decreased, and tan δ (dielectric tangent) decreased, resulting in the improvement of reliability of the produced capacitor.