Method for forming a semiconductor device

A method for forming a semiconductor device, comprising:

• forming first and second semiconductor fins extending upwardly from a substrate;
• conformally forming a spacer layer over the first and second semiconductor fins;
• conformally forming a first dielectric layer over the spacer layer;
• after conformally forming the first dielectric layer, forming a flowable oxide layer laterally between the first and second semiconductor fins;
• conformally forming a second dielectric layer over the first dielectric layer and the flowable oxide layer, wherein the second dielectric layer has a portion laterally between the first and second semiconductor fins;
• performing a chemical-mechanical planarization (CMP) process on the first and second dielectric layers and the spacer layer, such that the first and second semiconductor fins are exposed;
• after performing the CMP process, thinning down the spacer layer;
• and
• after thinning down the spacer layer, forming a gate structure extending across the first and second semiconductor fins.

A method for forming a semiconductor device, comprising:

• depositing a first dielectric layer over a first fin and a second fin;
• depositing a dielectric dummy fin layer over the first dielectric layer, wherein the dielectric dummy fin layer has a first portion over top surfaces of the first fin and the second fin;
• depositing a second dielectric layer over the dielectric dummy fin layer;
• removing a first portion of the second dielectric layer over a top surface of the first portion of the dielectric dummy fin layer, wherein a second portion of the second dielectric layer remains between the first fin and the second fin;
• recessing the second portion of the second dielectric layer;
• removing the first portion of the dielectric dummy fin layer, wherein a second portion of the dielectric dummy fin layer remains between the first fin and the second fin;
• depositing a helmet layer over the recessed second portion of the second dielectric layer and the second portion of the dielectric dummy fin layer;
• depositing a third dielectric layer over the helmet layer;
• and
• removing the third dielectric layer, the helmet layer, the dielectric dummy fin layer, and the first dielectric layer over the top surfaces of the first fin and the second fin.