Punch-through diode steering element

A method of forming a non-volatile storage device, the method comprising:

• forming a plurality of bit lines;
• forming a plurality of word lines;
• forming a plurality of memory cells, each of the memory cells residing between a first bit line of the plurality of bit lines and a first word line of the plurality of word lines, the forming the memory cells including:
• forming material for reversible resistivity-switching elements;
• forming a first region of semiconductor material that is heavily doped with an impurity having a first conductivity, the first region having a graded doping profile;
• forming a second region of semiconductor material that is lightly doped with an impurity having a second conductivity;
• forming a third region of semiconductor material that is heavily doped with an impurity having the first conductivity, the second region being between the first and third regions, the third region having a graded doping profile;
• and
• etching the material for reversible resistivity-switching elements, the first region of semiconductor material, the second region of semiconductor material, and the third region of semiconductor material to form memory cells having reversible resistivity-switching elements in series with diodes.

A method of forming a non-volatile storage device, the method comprising:

• forming bottom conductors;
• forming a first layer of a semiconductor material that is heavily doped with an impurity having a first conductivity;
• forming a second layer of a semiconductor material that is lightly doped with an impurity having a second conductivity;
• forming a third layer of a semiconductor material that is heavily doped with an impurity having the first conductivity, the second layer being between the first and third layers, the first layer having a doping concentration that gradually increases in a direction away from the second layer of semiconductor material, the third layer having a doping concentration that gradually increases in a direction away from the second layer of semiconductor material;
• forming a layer for bottom memory element electrodes;
• forming layer for reversible resistivity-switching elements;
• forming a layer for top memory element electrodes;
• and
• etching the first, second, and third layer of a semiconductor material, the layer for bottom memory element electrodes, the layer for reversible resistivity-switching elements, and the layer for top memory element electrodes to form memory cells having reversible resistivity-switching elements in series with diodes.