Method for fabricating a semiconductor device having an epitaxial channel and transistor having same
View Patent ↗A transistor having an epitaxial channel and a method for fabricating a semiconductor device having an epitaxial channel, the method including forming a hardmask on a substrate and forming an opening in the hardmask. The opening is geometrically characterized by a long dimension and a short dimension, and the opening is arranged in a predetermined manner relative to the channel region of a transistor. An epitaxial material is formed in the opening that induces strain in substrate regions proximate to the epitaxial material. The epitaxial material is confined to the opening, such that an epitaxial channel is formed. A transistor is fabricated in proximity to the epitaxial channel, such that the strain induced in the substrate provides enhanced transistor performance. By confining the epitaxial material to a predefined channel in the substrate, plastic strain relaxation of the epitaxial material is minimized and a maximum amount of strain is induced in the substrate.
1. A method for fabricating a semiconductor device, the method comprising:
providing a substrate having an active substrate region defined by isolation regions;
forming a gate structure on the substrate, the gate structure having a gate body with sidewall spacers thereon;
removing the gate body and exposing a channel region in the active substrate region that is defined by the sidewall spacers;
selectively forming an epitaxial region on the channel region, the epitaxial region spanning the active substrate region and projecting above the substrate, the epitaxial region having a relatively long lateral dimension in the channel width direction and self-aligned to the channel region,
wherein a lattice constant of the epitaxial region differs from a lattice constant of the substrate, such that strain is induced in regions of the substrate proximal to the epitaxial region;
forming a gate dielectric layer overlying the epitaxial region and the surface of the sidewall spacers;
conformally depositing a gate metal layer on the gate dielectric layer;
depositing a fill material over the gate metal layer and substantially filling an area between the sidewall spacers and the gate metal layer; and
planarizing the fill material, the gate metal layer, and the gate dielectric layer to form a gate electrode overlying the gate dielectric, the gate electrode having a relatively long lateral dimension substantially parallel to the relatively long lateral dimension of the epitaxial region.
2. The method of claim 1 further comprising forming a recess in the channel region, wherein a trench is defined by the sidewall spacers, and wherein selectively forming the epitaxial region comprises filling the recess.
3. The method of claim 1 , wherein forming a gate structure comprises:
forming an etch stop layer on the substrate;
forming the gate body by forming a patterned etchable material on the etch stop layer; and
forming the sidewall spacers on side surfaces of the patterned etchable material.
4. The method of claim 3 further comprising forming source and drain regions in the substrate on both side of the gate structure.
5. The method of claim 1 , wherein removing the gate body comprises removing the gate body to form a gate pattern on the substrate defined by the sidewall spacers.
6. The method of claim 1 , wherein the method is sequentially repeated to form both N-type and P-type semiconductor devices on the substrate.
7. The method of claim 1 , wherein forming a gate dielectric layer comprises forming a high-K dielectric layer.