High-density semiconductor device

A semiconductor device, the comprising:

• a substrate;
• a first material formed on the substrate;
• a second material formed on the substrate;
• and
• a plurality of fins formed from the substrate under the first and second materials;
• wherein the first and second materials are formed on the substrate by
• (1) forming above the substrate a spacer that has opposite first and second sidewalls,
• (2) depositing the first material on the first and second sidewalls of the spacer,
• (3) depositing a spacer material on the first material, and
• (4) converting the first material on the second sidewall of the spacer into the second material.

A method comprising:

• forming above a substrate a spacer that has opposite first and second sidewalls;
• depositing a first material on the first and second sidewalls of the spacer;
• depositing a spacer material on the first material;
• converting the first material on the second sidewall of the spacer into a second material;
• etching the substrate to fabricate fins under the first and second materials;
• and
• fabricating a transistor that includes one of the fins.