Method for forming an extended metal gate using a damascene process

A method for forming an extended metal gate and a self-aligned contact comprising the steps of:

• a. providing a semiconductor structure (11);
• said semiconductor structure having a gate dielectric layer thereon;
• said gate dielectric layer having a gate silicon layer thereon;
• said gate silicon layer having a doped silicon oxide layer thereon;
• said doped silicon oxide layer having a disposable gate layer thereon;
• b. patterning said disposable gate layer;
• said doped silicon oxide layer, said gate silicon layer, said gate dielectric layer and semiconductor structure to form trenches for shallow trench isolation;
• c. forming shallow trench isolation (STI) structures by depositing and planarizing a first dielectric layer in the trenches;
• d. patterning said disposable gate layer, said doped silicon oxide layer, said gate silicon layer and said gate dielectric layer to form gate structure having sidewalls;
• e. forming dielectric spacers on said sidewalls of said gate structure;
• f. forming a gapfill layer over said semiconductor structure and said gate structure and planarizing said gapfill layer stopping on said disposable gate layer;
• g. forming a silicon nitride layer on said disposable gate layer and said gapfill layer;
• h. forming a second dielectric layer over said silicon nitride layer;
• i. patterning said second dielectric layer to form a trench over said gate structure;
• said trench having a width greater than the width of said gate structure;
• j. removing said silicon nitride layer in a bottom of said trench;
• k. removing said disposable gate layer;
• whereby said doped silicon oxide layer is exposed;
• l. removing said doped silicon oxide layer using an etch selective to undoped silicon oxide;
• whereby said gate silicon layer is exposed;
• m. forming a barrier layer over said gate silicon layer;
• and
• n. forming a metal gate layer on said barrier layer.