Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising:

• defining a plurality of active regions in a substrate;
• forming at least one dielectric layer on the substrate;
• forming a plurality of openings in the at least one dielectric layer and exposing the plurality of active regions;
• introducing a first oxygen plasma and a first fluorine plasma to remove by-products in the plurality of openings and oxidize inner surfaces of the plurality of openings;
• introducing a second oxygen plasma and a second fluorine plasma to remove the oxidized inner surfaces for enlarging the plurality of openings and to repair the plurality of active regions;
• introducing a third oxygen plasma to oxidize inner surfaces of the enlarged plurality of openings to form an oxide layer;
• removing the oxide layer to form a plurality of contact holes, wherein a cross-sectional structure of two adjacent contact holes comprises a capital, a base, and a shaft between the capital and the base, and a width of the shaft is smaller than a width of the base and smaller than a width of the capital;
• depositing a conductive material on the substrate and filling the plurality of contact holes;
• and
• planarizing the conductive material to form a plurality of contacts in the plurality of contact holes.