Semiconductor structures and methods of fabrication of same

A method of fabricating a flash memory device, the method comprising:

• forming an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, the etch stop material comprising an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide in contact with the stack, wherein the stack of alternating insulating materials and first conductive materials is a stack of alternating first oxide materials and first polysilicon materials;
• forming an opening through the stack and the etch stop material;
• removing portions of the first polysilicon materials to create a plurality of first recesses adjacent the first polysilicon materials;
• selectively removing a portion of the amorphous aluminum oxide to form a second recess adjacent the amorphous aluminum oxide;
• forming a second oxide material on sidewalls of the first polysilicon material in the plurality of first recesses;
• forming a nitride material substantially conformally in the opening and forming a third oxide material over the nitride material to fill the second recess;
• filling the plurality of first recesses with a second conductive material to form a plurality of floating gates, the second conductive material comprising polysilicon;
• and
• forming a channel material extending through the stack of alternating insulating materials and first conductive materials and into at least a portion of the etch stop material,
• wherein filling the plurality of first recesses with the second conductive material comprises forming the second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, without forming the second conductive material between the channel material and the etch stop material.

A semiconductor structure, comprising:

• an etch stop material between a substrate and a stack of alternating insulating materials and first conductive materials, the etch stop material comprising an amorphous aluminum oxide on the substrate and a crystalline aluminum oxide on the amorphous aluminum oxide;
• a channel material extending through the stack and into at least a portion of the etch stop material;
• and
• a second conductive material between the channel material and at least one of the first conductive materials in the stack of alternating insulating materials and first conductive materials, wherein the second conductive material is not between the channel material and the etch stop material.