Microelectronic devices and memory devices including conductive levels having varying compositions

A memory device comprising:

• a stack structure comprising sequential conductive levels and insulative levels arranged in tiers within a stack structure;
• strings of memory cells vertically extending through the stack structure, portions of the conductive levels laterally neighboring the strings of memory cells individually comprising a conductive liner material contacting vertically neighboring insulative levels and a conductive material in contact with the conductive liner material;
• and
• slot structures vertically extending through the stack structure, portions of the conductive levels laterally neighboring the slot structures individually comprising tungsten directly contacting vertically neighboring insulative levels.

A microelectronic device, comprising:

• a stack structure comprising tiers each comprising a conductive level and an insulative level vertically neighboring the conductive level, each conductive level comprising:
• a first conductive structure;
• and
• a second conductive structure laterally neighboring the first conductive structure and comprising grains having a larger grain size than the first conductive structure;
• and
• vertical strings of memory cells vertically extending through the stack structure.