Patent ID: 7479452

Claim:
A method of forming contact plugs, comprising: forming a dielectric layer on a semiconductor substrate with a first region and a second region; forming a mask layer on the dielectric layer; forming at least one first contact in the mask layer and the dielectric layer at the first region; forming openings in the mask layer at the second region to expose the dielectric layer; forming polysilicon spacers on sidewalls of the openings and partially filling polysilicon in the first contact at the same time, wherein the polysilicon spacers are formed by first depositing a doped polysilicon layer and then etching back the doped silicon layer; patterning the dielectric layer exposed by the openings to form a second contact and a third contact within the openings; partially etching back the dielectric layer to form a trench around each of the second contact and the third contact by using the mask layer and the polysilicon spacers as an etching mask; and forming contact plugs in the first contact, the second contact, and the third contact.