Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Patent
1999-01-22
2000-08-01
Carroll, J.
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
257295, 257310, 257410, 257411, H01L 29788
Patent
active
060970588
ABSTRACT:
A ferroelectric layer having a low dielectric constant which is used for a ferroelectric memory element is provided. Also, the ferroelectric layer having a high melting point used for the ferroelectric memory element is provided. An FET 20 has a stacked structure including a gate oxidation layer 24, a floating gate 26, a ferroelectric layer 28, and a control gate 30 deposited on a channel region CH in that order, the channel region CH being formed in a semiconductor substrate 22 made of silicon. The ferroelectric layer 28 consists of a thin film made of a mixed crystal composed of Sr.sub.2 (Ta.sub.1-x Nb.sub.x).sub.2 O.sub.7. The crystal structure of both Sr.sub.2 Nb.sub.2 O.sub.7 and Sr.sub.2 Ta.sub.2 O.sub.7 is pyramid quadratic structure, and their lattice constants are similar to each other. Their relative dielectric constants are low, and their melting points are high. Curie temperature related with their ferroelectricity is, however, too high in Sr.sub.2 Nb.sub.2 O.sub.7 and too low in Sr.sub.2 Ta.sub.2 O.sub.7. In order to overcome the discrepancies, the ferroelectric layer 28 having desired curie temperature is formed with a mixed crystal made of Sr.sub.2 (Ta.sub.1-x Nbx).sub.2 O.sub.7.
REFERENCES:
The 43th Preprints of the Joint Congress of applied Physics (1996) No. 2 p. 409.
Technical Research Report of IEICE (1993) vol. 93 No. 350, pp. 53-59.
Nanamatsu, et al.; "Crystallographic and Dielectric Properties of Ferroelectric A.sub.2 B.sub.2 O.sub.7 (A=Sr B=Ta, Nb) Crystals and Their Solid Solutions"; Journal of the Physical Society of Japan; Mar. 1975; vol. 3, No. 3, pp. 817-824.
Fujimori Yoshikazu
Nakamura Takashi
Carroll J.
Rohm & Co., Ltd.
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