Integrated circuit structure and method for preparing the same

A method for preparing an integrated circuit structure, comprising:

• forming a conductive layer over a substrate;
• forming a dielectric layer over the conductive layer;
• patterning the dielectric layer and the conductive layer to form a first dielectric structure, a second dielectric structure, a first conductive structure and a second conductive structure, wherein a first opening is formed between the first dielectric structure and the second dielectric structure, and a second opening is formed between the first conductive structure and the second conductive structure;
• partially removing the first conductive structure and the second conductive structure to form an enlarged second opening;
• forming an inter-layer dielectric (ILD) layer covering sidewalls of the first dielectric structure and the second dielectric structure;
• forming a reinforcement pillar of energy removable material in the ILD layer;
• forming a capping dielectric layer over the reinforcement pillar;
• and
• performing a thermal process to transform the reinforcement pillar into a dielectric isolation structure including a liner layer enclosing an air gap.