Self-Aligned Semiconductor Fabrication With Fosse Features

A method for patterning a target layer on a semiconductor substrate, the method comprising:

• forming a first line, a spacer, and a first material layer over the target layer, wherein the spacer surrounds the first line, and the first material layer surrounds the spacer;
• removing the spacer to form a fosse pattern trench surrounding the first line;
• and
• transferring the fosse pattern trench into the target layer to form a fosse feature trench in the target layer, wherein the fosse feature trench surrounds a first portion of the target layer that is underneath a protection layer.

A method for patterning a target layer on a semiconductor substrate, the method comprising:

• forming a first line over the target layer, wherein the first line includes a patterning layer portion over a hard mask layer portion;
• forming a spacer around the first line;
• depositing a spacer-surrounding material layer, the spacer-surrounding material layer surrounding the spacer;
• removing the spacer to form a fosse pattern trench surrounding the first line;
• etching the target layer through the fosse pattern trench thereby forming a first trench in the target layer;
• and
• after the etching of the target layer, removing the patterning layer portion and the spacer-surrounding material layer while keeping the hard mask layer portion over a first portion of the target layer, the first portion of the target layer being surrounded by the first trench.