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 transistor, the transistor characterized by a channel length and a channel width, the method comprising:
providing a substrate having an active substrate region defined by isolation regions, the active region defined by a lateral channel length direction and a lateral channel width direction substantially orthogonal to the lateral channel length direction;
forming a hardmask overlying the substrate and forming an opening in the hardmask exposing a portion of the active substrate region;
forming an epitaxial region in the opening spanning the active substrate region and projecting above the substrate, the epitaxial region having a relatively long lateral dimension in the channel length direction and a relatively short lateral dimension in the channel width direction,
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
forming a gate electrode strip overlying the gate dielectric layer, the gate electrode strip having a relatively long lateral dimension substantially orthogonal to the relatively long lateral dimension of the epitaxial region.
2. The method of claim 1 , wherein forming a hardmask comprises forming a dielectric layer overlying the substrate.
3. The method of claim 2 further comprising forming a recess in the substrate defined by the opening, wherein forming an epitaxial region in the opening comprises at least filling the recess.
4. The method of claim 3 further comprising removing the hardmask prior to forming the gate dielectric layer.
5. A method for fabricating a semiconductor device, the method comprising:
providing a substrate having an active substrate region defined by isolation regions, the active region further defined by a lateral channel length direction and a lateral channel width direction substantially orthogonal to the lateral channel length direction;
forming a hardmask overlying the substrate and forming an opening in the hardmask exposing a portion of the active substrate region;
forming a recess in the substrate defined by the opening;
forming an epitaxial pillar region in the recess spanning the active substrate region, the epitaxial pillar region having a relatively long lateral dimension in the channel length direction and a relatively short lateral dimension in the channel width direction,
wherein a lattice constant of the epitaxial pillar region differs from a lattice constant of the substrate, such that strain is induced in regions of the substrate proximal to the epitaxial pillar region;
removing the hardmask and leaving a portion of the epitaxial pillar region projecting above the substrate;
forming a gate dielectric layer overlying the epitaxial pillar region; and
forming a gate electrode strip overlying the gate dielectric layer, the gate electrode having a relatively long lateral dimension substantially orthogonal to the relatively long lateral dimension of the epitaxial pillar region.
6. The method of claim 5 , wherein forming an epitaxial pillar region in the opening comprises at least filling the recess.
7. The method of claim 5 , wherein forming an epitaxial pillar region comprises epitaxially forming silicon and germanium, a silicon germanium alloy, or a III-V semiconductor material.