Patent ID: 6118692
Filing Date: 2000-09-12
Classification: G11C

Abstract:
An electrically alterable non-volatile multi-level memory device including a plurality of non-volatile multi-level memory cells, comprising:wherein an operation for settling a parameter of at least one non-volatile multi-level memory cell of the plurality of non-volatile multi-level memory cells to one state selected from a plurality of states including at least a first state, a second state, a third state and a fourth state is carried out in response to information to be stored in the one non-volatile multi-level memory cell, andwherein thereafter an operation for reading status of the one non-volatile multi-level memory cell by comparing the parameter with a plurality of reading reference parameters including at least a first reading reference parameter, a second reading reference parameter and a third reading reference parameter,wherein a conductivity value of the one non-volatile multi-level memory cell is decreased in order of the first state, the second state, the third state and the fourth state,wherein the first reading reference parameter is allocated between the first state and the second state, the second reading reference parameter is allocated between the second state and the third state, and the third reading reference parameter is allocated between the third state and the fourth state, andwherein the second reading reference parameter is allocated substantially at a midpoint of the second state and the third state, and the first reading reference parameter is allocated adjacent to the second state from a midpoint of the first state and the second state.