Microelectronic devices with nitrogen-rich insulative structures

A microelectronic device, comprising:

• a stack structure including an array region and a peripheral region horizontally neighboring the array region, the stack structure comprising:
• a first region comprising first levels respectively comprising:
• silicon oxide material within the array region and the peripheral region;
• within the array region, conductive material vertically adjacent the silicon oxide material;
• and
• within the peripheral region, silicon nitride material vertically adjacent the silicon oxide material and having a first refractive index and a first ratio of nitrogen atoms to silicon atoms greater than about 1.60:1.00;
• and
• a second region vertically overlying the first region and including second levels respectively comprising:
• the silicon oxide material within the array region and the peripheral region;
• within the array region, the conductive material vertically adjacent the silicon oxide material;
• and
• within the peripheral region, additional silicon nitride material vertically adjacent the silicon oxide material, the additional silicon nitride material having a second refractive index greater than the first refractive index and having a second ratio of nitrogen atoms to silicon atoms less than about 1.60:1.00;
• and
• a third region vertically overlying the second region and including third levels respectively comprising:
• the silicon oxide material within the array region and the peripheral region;
• within the array region, the conductive material vertically adjacent the silicon oxide material;
• and
• within the peripheral region, the silicon nitride material vertically adjacent the silicon oxide material;
• and
• strings of memory cells vertically extending through the stack structure and horizontally confined within the array region of the stack structure.