Semiconductor device structure and methods of forming the same

A method, comprising:

• forming first, second, and third fin structures over a substrate;
• depositing a liner layer around the first, second, and third fin structures;
• depositing a dielectric layer between the first and second fin structures and between the second and third fin structures, wherein a seam is formed in the dielectric layer between the first and second fin structures;
• removing portions of the dielectric layer between the first and second fin structures to expose the seam and between the second and third fin structures to expose the liner layer;
• depositing an insulation material to embed the first, second, and third fin structures, wherein the insulation material is in contact with the liner layer between the second and third fin structures, and the seam between the first and second fin structures is filled with the insulation material;
• implanting a dopant into the insulation material between the first and second fin structures;
• and
• performing an etch process, wherein the insulation material between the first and second fin structures is etched at a slower rate than the insulation material between the second and third fin structures.

A method, comprising:

• forming first, second, and third fin structures over a substrate, wherein a first trench having a first width is formed between the first and second fin structures, and a second trench having a second width substantially greater than the first width is formed between the second and third fin structures;
• depositing a first dielectric layer in the first and second trenches, wherein a seam is formed in the first dielectric layer in the first trench, and the first dielectric layer is a conformal layer;
• removing portions of the first dielectric layer in the first and second trenches, wherein the seam in the first trench is exposed;
• depositing a second dielectric layer in the first and second trenches, wherein the seam in the first trench is filled with the second dielectric layer, and a dielectric wall comprising the first and second dielectric layers is formed in the first trench;
• removing the first and second dielectric layers in the second trench, wherein a top surface of the dielectric wall is located below a level of a top surface of the first fin structure;
• and
• forming a shallow trench isolation region in the second trench.