Semiconductor memory devices

A semiconductor device comprising:

• gate electrodes on a substrate, the gate electrodes being spaced apart from each other in a vertical direction substantially perpendicular to an upper surface of the substrate;
• and
• a memory channel structure extending through the gate electrodes in the vertical direction on the substrate,
• wherein the memory channel structure includes:
• a filling pattern structure extending in the vertical direction;
• a channel on a sidewall of the filling pattern structure;
• and
• a charge storage structure on a sidewall of the channel,
• wherein the filling pattern structure includes:
• a first filling pattern having a pillar shape and including a material having a thermal conductivity equal to or more than about 100 W/m·K at a temperature of 25° C., the first filling pattern being a single layer;
• and
• a second filling pattern on and contacting an outer sidewall of the first filling pattern, the second filling pattern including a material having a thermal conductivity less than that of the first filling pattern,
• wherein the second filling pattern has a cup-like shape and
• wherein the channel contacts a sidewall of the second filling pattern.

A semiconductor device comprising:

• a gate electrode structure on a 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 memory channel structure extending through the gate electrode structure in the vertical direction on the substrate;
• and
• wherein the memory channel structure includes:
• a first filling pattern extending in the vertical direction and having a cup-like shape;
• a second filling pattern at contacts an inner sidewall of the first filling pattern and fills a central space formed by the first filling pattern;
• a channel contacting an outer sidewall of the first filling pattern;
• and
• a charge storage structure on a sidewall of the channel, and
• wherein the first filling pattern includes a material having a thermal conductivity equal to or more than about 100 W/m·K at a temperature of −25° C.