Methods of fabricating memory device with spaced-apart semiconductor charge storage regions

A method of making a monolithic three dimensional NAND string, comprising:

• forming a stack of alternating layers of a first material and a second material different than the first material over a substrate;
• etching the stack to form a front side opening in the stack having a sidewall defined at least partially by the alternating layers of the first material and the second material;
• removing a first portion of the second material layers through the front side opening to form front side recesses between the first material layers;
• selectively forming vertically spaced apart charge storage regions comprising a semiconductor material on the second material layers;
• forming a tunnel dielectric layer over the charge storage regions in the front side opening;
• and
• forming a semiconductor channel over the tunnel dielectric layer in the front side opening,
• wherein the vertically spaced apart charge storage regions comprise a semiconductor material deposited within the front side recesses, wherein forming the vertically spaced apart charge storage regions comprises:
• forming a first layer of the semiconductor material over the first material layers exposed on the sidewall of the front side opening and over the second material layers exposed within the front side recesses, wherein a thickness of the first layer of semiconductor material formed over the second material layers is greater than a thickness of the first layer of semiconductor material formed over the first material layers due to a difference in an incubation time for the semiconductor material on the first material relative to an incubation time for the semiconductor material on the second material;
• and
• etching through the front side opening to remove first portions of the semiconductor material from over the first material layers on the sidewall of the front side opening to leave vertically spaced apart second portions of the semiconductor material within the front side recesses;
• forming a second layer of the semiconductor material over the first material layers exposed on the sidewall of the front side opening and over second portions of the first layer of semiconductor material within the front side recesses;
• and
• etching through the front side opening to remove first portions of the second layer of semiconductor material from over the first material layers on the sidewall of the front side opening, wherein the vertically spaced apart charge storage regions comprising the semiconductor material fill entire volumes of the first side recesses, and each of the vertically spaced apart charge storage regions includes a respective vertical sidewall that is physically exposed to an unfilled volume of the front side opening and continuously extends between, and is adjoined to, a sidewall of a respective overlying layer of the first material and a sidewall of a respective underlying layer of the first material.