Etch profile control of gate contact opening

Abstract

A method comprises forming a gate structure between gate spacers; etching back the gate structure to fall below top ends of the gate spacers; forming a gate dielectric cap over the etched back gate structure; performing an ion implantation process to form a doped region in the gate dielectric cap; depositing a contact etch stop layer over the gate dielectric cap and an ILD layer over the contact etch stop layer; performing a first etching process to form a gate contact opening extending through the ILD layer and terminating prior to reaching the doped region of the gate dielectric cap; performing a second etching process to deepen the gate contact opening, wherein the second etching process etches the doped region of the gate dielectric cap at a slower etch rate than etching the contact etch stop layer; and forming a gate contact in the deepened gate contact opening.