Method of manufacturing three-dimensional semiconductor device and variable resistive memory device

A method of manufacturing a variable resistive memory device, the method comprising:

• forming a source on a semiconductor substrate;
• sequentially forming a first semiconductor layer formed of a first material, a second semiconductor layer formed of a second material having a higher oxidation rate than that of the first material, and a third semiconductor layer formed of the first material, on the source;
• patterning the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer;
• forming a lightly doped drain (LDD) region in the second semiconductor layer and a drain in the third semiconductor layer;
• oxidizing outer circumferences of the first semiconductor layer, the LDD region and the drain region to form a gate insulating layer;
• forming a gate on an outer circumference of the gate insulating layer to overlap the first semiconductor layer and a portion of the LDD region;
• forming a heating electrode on the drain;
• and
• forming a variable resistance layer on the heating electrode.

A method of manufacturing a variable resistive memory device, the method comprising:

• forming a pillar including a channel region, a LDD region and a drain region on a semiconductor substrate including a source region;
• forming a gate insulating layer on outer circumference of the pillar, wherein a thickness of the gate insulating layer which overlaps the LDD region is thicker than a thickness of the gate insulating layer which overlaps the channel region;
• forming a gate on an outer circumference of the gate insulating layer:
• forming a heating electrode on the drain;
• and
• forming a variable resistance layer on the heating electrode.