Patent ID: 8441837
Filing Date: 2013-05-14
Classification: G11C,H01L

Abstract:
1. A variable resistance nonvolatile memory device comprising: a plurality of memory cells in each of which a variable resistance element and a current steering element having two terminals are connected in series, said variable resistance element changing, by application of a first voltage having a predetermined first polarity, to a low resistance state with a resistance value in a first range, and changing, by application of a second voltage having a second polarity opposite to the first polarity, to a high resistance state with a resistance value in a second range higher than the first range; a plurality of first signal lines and a plurality of second signal lines crossing said first signal lines; a memory cell array in which said memory cells are arranged at cross-points of said first signal lines and said second signal lines and each of said memory cells has ends connected to a set of one of said first signal lines and one of said second signal lines which crosses said first signal line; a write circuit which generates a bipolar voltage to be applied to said memory cells through said first signal lines and said second signal lines; and a current limit circuit placed in a path of a current flowing from said write circuit to said memory cells, said current limit circuit limiting only the current flowing in a direction for changing said memory cells to the low resistance state, wherein in each of said memory cells, said variable resistance element comprises: a first electrode; a second electrode; and a variable resistance layer placed between and in contact with said first electrode and said second electrode, said variable resistance layer contains an oxide of metal as a primary variable resistance material, said first electrode and said second electrode are made of materials of different elements, and relations V wherein each of said memory cells changes to the low resistance state when the first voltage having the first polarity such that said first signal line has a higher voltage than said second signal line is applied to said memory cell through said first signal line and said second signal line connected to said memory cell, and each of said memory cells changes to the high resistance state when the second voltage having the second polarity opposite to the first polarity is applied to said memory cell through said first signal line and said second signal line connected to said memory cell, said write circuit comprises: a first drive circuit which generates a first drive voltage equal to or higher than the first voltage; a second drive circuit which generates a second drive voltage equal to or higher than the second voltage; a third drive circuit which generates a voltage serving as a basis for the first drive voltage; and a fourth drive circuit which generates a voltage serving as a basis for the second drive voltage, said variable resistance nonvolatile memory device further comprises: a first selection circuit which connects said first drive circuit and said fourth drive circuit to a selected one of said first signal lines; and a second selection circuit which connects said second drive circuit and said third drive circuit to a selected one of said second signal lines, and said current limit circuit is placed between said first drive circuit and said first selection circuit.