Semiconductor device and method of forming vertical structure

A method of forming a vertical structure, comprising:

• providing a substrate;
• providing a vertical structure over the substrate;
• and
• providing a first barrier layer over a source of the vertical structure to protect the source during formation of a first oxide layer corresponding to the source.

A method of forming a vertical structure with at least two barrier layers, comprising:

• providing a substrate;
• providing a vertical structure including a source, a channel, and a drain over the substrate;
• providing a first barrier layer over the source, the channel, and the drain;
• etching the first barrier layer to expose the channel and the drain;
• providing a gate over the channel;
• and
• providing a second barrier layer over the gate and the drain.