Semiconductor device and manufacturing method thereof

Abstract

A method includes forming first and second gate stacks extending across a semiconductor fin on a substrate; forming source/drain regions in the semiconductor fin, wherein one of the source/drain region is between the first and second gate stacks; forming a dielectric layer laterally surrounding the first and second gate stacks; doping a portion of the dielectric layer between the first and second gate stacks with a dopant; removing the second gate stack to form a gate trench next to the doped first portion of the dielectric layer; performing an annealing process to expand the doped first portion of the dielectric layer toward the gate trench; forming an isolation structure in the gate trench and next to the expanded first portion of the dielectric layer; forming a source/drain contact extending through the dielectric layer to the one of the source/drain regions.