Semiconductor device structure with boron- and nitrogen-containing material and method for forming the same

A method for forming a semiconductor device structure, comprising:

• providing a substrate having a base and a fin over the base;
• forming a nanostructure stack over the fin, wherein the nanostructure stack comprises a first nanostructure and a second nanostructure sequentially formed over the fin;
• forming a gate stack over the nanostructure stack and the fin;
• partially removing the nanostructure stack and the fin, which are not covered by the gate stack, to form a trench in the nanostructure stack and the fin;
• removing an end portion of the first nanostructure through the trench to form a recess in the nanostructure stack, wherein the recess is between the fin and the second nanostructure;
• forming an inner spacer in the recess using a first precursor, wherein the first precursor comprises a first boron- and nitrogen-containing material having a first hexagonal ring structure, the inner spacer has a plurality of first layers, and each first layer comprises boron and nitrogen;
• replacing the gate stack with a metal gate stack, wherein the metal gate stack comprises a gate dielectric layer, a work function metal layer, and a gate electrode layer, and the gate electrode layer is over the work function layer;
• removing an upper portion of the metal gate stack;
• and
• forming a cap layer over the metal gate stack using a second precursor after the upper portion of the metal gate stack is removed, wherein the second precursor comprises a boron-, nitrogen-, and carbon-containing material having a second hexagonal ring structure, the cap layer has a plurality of second layers, and each second layer comprises boron, nitrogen, and carbon, wherein the work function layer is closer to the cap layer than the gate dielectric layer.

A semiconductor device structure, comprising:

• a substrate;
• a gate stack over the substrate, wherein the gate stack comprises a gate dielectric layer, a work function metal layer, and a gate electrode layer, and the gate electrode layer is over the work function layer;
• a spacer over first sidewalls of the gate stack, wherein the spacer has a plurality of first layers, each first layer comprises a first boron- and nitrogen-containing material having a first hexagonal ring structure, and one of the first layers is substantially parallel to the first sidewall of the gate stack;
• and
• a cap layer over the gate stack and laterally surrounded by the spacer, wherein the cap layer has a plurality of second layers, each second layer comprises a boron-, nitrogen-, and carbon-containing material having a second hexagonal ring structure, and one of the second layers is substantially perpendicular to one of the first layers, wherein the work function layer extends upward along the spacer to reach the cap layer.