US Patent 10096518 Semiconductor structures and fabrication methods thereof

Semiconductor structure and fabrication method thereof are provided. An exemplary method includes providing a semiconductor substrate including a plurality of first fin structures, each having a first width, and a plurality of second fin structures, each having a second width greater than the first width. The method further includes forming a first isolation film covering sidewall surfaces of the first fin structures and the second fin structures, forming a trench in the first isolation film to expose at least a top portion of at least one sidewall surface of one or more second fin structures, forming an isolation fluid layer to fill the trenches, and performing an oxygen annealing process to convert a surface layer of the top portion of the at least one sidewall surface of the one or more second fin structures into a by-product layer, and to convert the isolation fluid layer into a second isolation film.