Patent ID: 7372743
Filing Date: 2008-05-13
Classification: G11C

Abstract:
1. In a nonvolatile storage device comprising a memory cell including first and second diffusion layers and an insulating trapping layer located close to the first and second diffusion layers and having first and second trapping regions for trapping charges therein, a first dynamic reference cell having an equivalent structure to the memory cell wherein the first trapping region of the first dynamic reference cell is set in a charge accumulated state, and a second dynamic reference cell having an equivalent structure to the memory cell wherein the first trapping region of the second dynamic reference cell is set in a charge depleted state, a method for initializing the first and second dynamic reference cells when a data storage operation stores one-bit data in accordance with the presence or absence of charges in the first trapping region of the memory cell, the method comprising the steps of: presetting the second trapping regions of the memory cell, first and second dynamic reference cells into the charge accumulated state; and setting the first trapping region of the first dynamic reference cell into the charge accumulated state in accordance with the data storage operation of the memory cell after the presetting step.