High-k dielectric material stacks are considered to be a good candidate for tunnel barrier, replacing single SiO2 tunnel dielectrics in non-volatile flash memory. The use of low-k/high-k tunnel barriers was expected to enhance the electric field sensitivity with possibility of the reduction in operation voltage for Flash devices. In this work, we investigated the physical properties of (HfO2)(x)(SiO2)(1-x) with various compositions in conjunction with the tunneling characteristics of (HfO2)(x)(SiO2)(1-x)/SiO2 double dielectric structure for the application to charge trap flash memory(CTF) devices. The band-engineered (HfO2)(x)(SiO2)(1-x)/SiO2 double dielectric structure showed enhanced tunneling current above 2 V, while showed smaller tunneling current below 2 V because of increasing physical thickness of designed double layer structures. The band-engineered charge trap (CTD) device with (HfO2)(x)(SiO2)(1-x)/SiO2 double dielectric structure showed faster program/erase speed and larger memory window at same time and voltage compared to the CTD with a single SiO2 tunnel barrier. (C) 2011 Elsevier B. V. All rights reserved.