A nonvolatile ferroelectric memory device with a floating gate

Abstract

An adaptive ferroelectric field-effect transistor (FET) with a floating gate has been developed using a thin film of lead titanate ( PbTiO3) deposited on a n/p+ substrate by rf sputtering. This device utilizes the charge storage on the floating gate to control the n layer conductivity of a n/p+ Si substrate and performs a memory function, in which the drain conductance changes in proportion to the charge storage density on the floating gate. The device is a bulk channel field transistor structure and different from the conventional surface channel-type floating gate memory device. Thus, it possesses higher mobility and fast access time (<160 ns). The FET has low write/erase voltages (≤10 V) and its write/erase cycles are more than 106.