Microelectronic devices including back gate structures and back gate plates, and related memory devices and electronic systems

A method of forming a microelectronic device, comprising:

• forming a memory array structure comprising:
• forming an array channel region having volatile memory cells within a horizontal area of the array channel region, the volatile memory cells respectively comprising a vertical channel access device;
• and
• forming back gate structures horizontally interposed between neighboring vertical channel access devices and extending in a first horizontal direction;
• forming digit line structures vertically overlying the vertical channel access devices of the volatile memory cells;
• and
• forming a back gate plate within an edge of array region of the microelectronic device to contact the back gate structures of the memory array structure and at least partially vertically overlap with the digit line structures.

A microelectronic device, comprising:

• a memory array structure comprising:
• an array region comprising vertical channel access devices of memory cells within a horizontal area thereof;
• and
• back gate structures extending through the array region and between neighboring vertical channel access devices;
• digit line structures vertically overlying the vertical channel access devices of the memory cells;
• an edge of array region proximate a horizontal boundary of the memory array structure;
• and
• a back gate plate formed within the edge of array region, in contact with the back gate structures of the memory array structure, and at least partially vertically overlapping with the digit line structures.