Vertical memory devices

A vertical memory device, comprising:

• a substrate including an impurity region doped with carbon or p-type impurities;
• a channel structure on the substrate,
• the channel structure including a lower channel on an upper surface of the impurity region of the substrate and an upper channel contacting an upper surface of the lower channel,
• the lower channel having a slanted sidewall with respect to an upper surface of the substrate,
• the lower channel having a pillar shape,
• the upper channel having a slanted sidewall with respect to the upper surface of the substrate, and
• the upper channel having a hollow cylindrical shape;
• a charge storage structure covering an outer sidewall of the upper channel, a width of an upper surface of the charge storage structure being less than a maximum width of the lower channel;
• and
• a gate electrode structure on the substrate,
• the gate electrode structure including gate electrodes spaced apart from each other in a vertical direction substantially perpendicular to the upper surface of the substrate, each of the gate electrodes covering an outer sidewall of the channel structure or the charge storage structure.

A vertical memory device, comprising:

• a substrate including an impurity region at an upper portion of the substrate;
• a gate electrode structure on the substrate, the gate electrode structure including gate electrodes spaced apart from each other in a vertical direction substantially perpendicular to an upper surface of the substrate;
• and
• a channel on the substrate,
• the channel extending in the vertical direction on the substrate through the gate electrode structure and an upper portion of the impurity region of the substrate,
• the channel including a plurality of portions sequentially stacked in the vertical direction and connected with each other,
• each of the plurality of portions having a slanted sidewall with respect to the upper surface of the substrate,
• a width of an upper surface of a first portion among the plurality of portions of the channel disposed at an odd-numbered level from the upper surface of the substrate is greater than a width of an upper surface of a second portion among the plurality of portions of the channel directly above the first portion.