Thin-film dielectric and thin-film capacitor element
A thin-film dielectric having a higher dielectric constant than usual ones and not requiring a special single crystal substrate, and a large-capacity thin-film capacitor element using the thin-film dielectric, in which a BaTiO 3 -based perovskite solid solution and a KNbO 3 -based perovskite solid solution are alternately formed to form a crystal structure gradient region where a lattice constant continuously changes at the interface, and thus crystal lattice strain occurs, thereby permitting the production of a thin-film dielectric having a high dielectric constant; also, a large-capacity thin-film capacitor element can be produced by using the thin-film dielectric of the present invention.
1. A thin-film dielectric comprising:
two or more layers, each layer containing a (Ba 1-x M x ) α (Ti 1-y N y )O 3 film (M is at least one of Sr and Ca, N is at least one of Zr and Hf, 0≤x≤0.4, 0≤y≤0.6, and 0.7≤α≤1.0) and a (K 1-w A w ) β (Nb 1-z Ta z )O 3 film (A is at least one of Na and Li, 0≤w≤0.6, 0≤z≤0.2, and 0.7≤β≤1.0), the (Ba 1-x M x ) α (Ti 1-y N y )O 3 film and the (K 1-w A w ) β (Nb 1-z Ta z )O 3 film being joined to each other, the (Ba 1-x M x ) α (Ti 1-y N y )O 3 films and the (K 1-w A w ) β (Nb 1-z Ta z )O 3 films being alternately formed,
wherein for each of said two or more layers, the (Ba 1-x M x ) α (Ti 1-y N y )O 3 film and the (K 1-w A w ) β (Nb 1-z Ta z )O 3 film have an interface between them that has a crystal structure gradient region where a lattice constant continuously changes due to lattice mismatching.
2. The thin-film dielectric according to claim 1 wherein a layer having a heterojunction between the (Ba 1-x M x ) α (Ti 1-y N y )O 3 film and the (K 1-w A w ) β (Nb 1-z Ta z )O 3 film is formed for each of said two or more layers.
3. A thin-film capacitor element comprising electrodes formed on both surfaces of the thin-film dielectric according to claim 1 .
4. A thin-film capacitor element comprising at least one internal electrode layer formed in the thin-film dielectric according to claim 1 .