Method for forming quadruple density sidewall image transfer (SIT) structures

A method for forming a quadruple density sidewall image transfer (SIT) structure comprising the steps of:

• forming oxide spacers on opposite sidewalls of a first mandrel including the steps of providing a starting structure including multiple layers;
• said multiple layers of said starting structure including a substrate, a gate dielectric layer, a gate conductor;
• an oxide hardmask layer, a poly etch stop layer, a first nitride layer, and a poly mandrel layer capped with a second, thinner nitride layer;
• said oxide spacers forming a second mandrel;
• forming sidewall spacers on opposite sidewalls of said oxide spacer second mandrel;
• and
• using a pattern of said sidewall spacers to form the quadruple density sidewall image transfer (SIT) structure.