Nonvolatile flash memory devices using CeO2 nanocrystal trapping layer for two-bit per cell applications

Shao Ming Yang*, Chao-Hsin Chien, Jiun Jia Huang, Tan Fu Lei

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


In this study, we demonstrated the characteristics of nonvolatile silicon oxide nitride oxide silicon (SONOS)-type memories using cerium oxide (CeO 2) nanocrystals as a charge storage agent. We observed that the shape of the formed CeO2 nanocrystals is nearly spherical and that their size is almost similar identical to their high density of 5 × 10 11 cm-2. Such CeO2 nanocrystals were formed by depositing a thin CeO2 film of ca. 2-3 nm thickness using an evaporater gun system and then rapid thermal annealing (RTA) in O2 ambient at 900°C for 1 min. The fabricated memory devices show good electrical properties in terms of a sufficiently large memory window (>2 V), program/erase (P/E) speed (0.1/1 ms), retention time up to 104 s with only 5% charge loss, and endurance after 105 cycles with small memory window narrowing and two-bit operation. These properties suggest that the nonvolatile SONOS-type memories with the CeO2 nanocrystal trapping agent can be applied in future flash memories.

Original languageEnglish
Pages (from-to)3291-3295
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number6 A
StatePublished - 6 Jun 2007


  • Cerium oxide
  • Flash memory
  • Nanocrystal
  • Retention
  • Trapping layer

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