Shallow trench isolation for integrated circuits

A method, comprising:

• patterning a semiconductor layer on a substrate to form spaced apart semiconductor islands;
• growing an oxide layer on sidewalls of the semiconductor islands;
• depositing a sacrificial layer on the oxide layer and on exposed portions of the semiconductor layer;
• depositing a dielectric layer on the sacrificial layer to surround the spaced apart semiconductor islands;
• selectively removing the sacrificial layer with a wet etching process to form a gap between the dielectric layer and the oxide layer alongside the sidewalls of the semiconductor islands, wherein a width of the gap is based on a thickness of the sacrificial layer;
• filling the gap with a porogen containing material;
• and
• treating the porogen containing material to form a porous material.

A method, comprising:

• patterning a semiconductor layer on a substrate to form spaced apart semiconductor islands;
• growing an oxide layer on sidewalls of the semiconductor islands;
• depositing a sacrificial layer on the oxide layer and exposed portions of the semiconductor layer;
• depositing a first dielectric layer on the sacrificial layer to surround the spaced apart semiconductor islands;
• selectively removing the sacrificial layer with a wet etching process to form a gap between the first dielectric layer and the oxide layer, wherein the gap is positioned alongside each sidewall of the semiconductor islands;
• and
• filling the gap with a second dielectric layer, wherein the second dielectric layer has a lower dielectric constant than the first dielectric layer.