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US 6,445,025 B2Granted
Semiconductor memory device and manufacturing method thereof
AssigneeHitachi, Ltd.
InventorsKazufumi Suenaga, Kiyoshi Ogata, Kazuhiko Horikoshi, Jun Tanaka, Hisayuki Kato, Keiichi Yoshizumi, Hisahiko Abe
Life of this patent
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Abstract
The present invention is a high quality semiconductor memory device using a ferroelectric thin film capacitor as a memory capacitor at a high manufacturing yield, the ferroelectric thin film of the capacitor is specified such that the relative standard deviation of crystal grain sizes is 13% or less, to thereby ensure a high remanent polarization value and a small film fatigue (large rewritable number).
Claims6
A semiconductor memory device using a ferroelectric thin film capacitor as a memory capacitor, said capacitor comprising:
- a stacked structure having at least a lower electrode, a ferroelectric thin film, and an upper electrode;
- wherein crystal grains of said ferroelectric thin film have columnar shapes elongated substantially in parallel to the thickness direction of said ferroelectric thin film, and a relative standard deviation of crystal grain sizes of said crystal grains within a plane having a normal line in the film thickness direction is in a range of 13% or less.
Dependencies are inferred from the claim text.