Electronic device using zirconate titanate and barium titanate ferroelectrics in insulating layer

• US 5,572,052 A
• Filed: 01/19/1995
• Issued: 11/05/1996
• Est. Priority Date: 07/24/1992
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Okudaira, Tomonori, Kashihara, Keiichiro, Itoh, Hiromi
• Primary Examiner(s): Crane, Sara W.
• Assistant Examiner(s): Tang, Alice W.
• Application Number:
  US08/374,890
• Time in Patent Office: 656 Days
• Field of Search: 257/295, 365/145, 365/149, 361/312, 361/313, 361/322
• US Class Current: 257/295
• CPC Class Codes: H01L 29/78391 the gate comprising a layer which is used for its ferroelectric properties
• CPC Class Codes: H01L 29/92 Capacitors having potential barriers
• CPC Class Codes: H01L 29/94 Metal-insulator-semiconductors, e.g. MOS
• CPC Class Codes: H10B 53/00 Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors

Abstract

In an electronic device using lead zirconate titanate (PZT) or lanthanum lead zirconate titanate (PLZT) as the main insulating material, a PZT film or a PLZT film is formed on a sub-insulating layer consisting essentially of lead titanate, lanthanum lead titanate, barium titanate, strontium titanate, barium strontium titanate, lead zirconate, or lanthanum lead zirconate. In an MIS structure, a semiconductor, the sub-insulating layer, the PZT film and metal are deposited in order. In a capacitor, the sub-insulating layer and the PZT film are sandwiched between a pair of electrodes. The sub-insulating layer improves crystallinity of PZT or PLZT, and the dielectric constant. An oxide of Pb, La, Zr or Ti can be added as the sub-insulating layer in order to further suppress current leakage.

Claims

1. An electronic device including a MIS structure, wherein said MIS structure comprises:

a silicon layer,

a sub-insulating layer formed directly on said silicon layer by CVD or sputtering, and consisting essentially of at least a compound selected from the group consisting of lead titanate, lanthanum lead titanate, barium titanate, strontium titanate, barium strontium titanate, lead zirconate, and lanthanum lead zirconate,

a main insulating layer formed directly on said sub-insulating layer by CVD or sputtering, and consisting essentially of zirconate titanate, and

a layer formed on said main insulating layer, and consisting essentially of a conductor,

wherein said main insulating layer has a perovskite type crystal structure, and exhibits ferroelectricity at ambient temperature, and wherein said sub-insulating layer consists essentially of barium titanate.

2. An electronic device including a MIS structure, wherein said MIS structure comprises:

a silicon layer,

a film formed directly on said silicon layer, and consisting essentially of a material selected from the group consisting of silicon oxide, silicon nitride, nitride oxide, TiO₂ and Ta₂ O₅,

a sub-insulating layer formed directly on said film by CVD or sputtering, and consisting essentially of at least a compound selected from the group consisting of lead titanate, lanthanum lead titanate, barium titanate, strontium titanate, barium strontium titanate, lead zirconate, and lanthanum lead zirconate,

a main insulating layer formed directly on said sub-insulating layer by CVD or sputtering, and consisting essentially of zirconate titanate and,

a layer formed on said main insulating layer, and consisting essentially of a conductor,

wherein said main insulating layer has a perovskite type crystal structure, and exhibits ferroelectricity at ambient temperature, and wherein said sub-insulating layer consists essentially of barium titanate.

3. An electronic device including a capacitor structure, wherein said capacitor structure comprises:

a first electrode consisting essentially of noble metal,

a sub-insulating layer formed directly on said first electrode by CVD or sputtering, and consisting essentially of at least a compound selected from the group consisting of lead titanate, lanthanum lead titanate, barium titanate, strontium titanate, barium strontium titanate, lead zirconate, and lanthanum lead zirconate,

a main insulating layer formed directly on said sub-insulating layer by CVD or sputtering, and consisting essentially of zirconate titanate, and

a second electrode formed on said main insulating layer, and consisting essentially of a conductor,

wherein said main insulating layer has a perovskite type crystal structure, and exhibits ferroelectricity at ambient temperature, and wherein said sub-insulating layer consists essentially of barium titanate.