Semiconductor device with strain-inducing regions and method thereof

A method for forming a MOSFET, comprising:

• providing a substrate having a first surface;
• forming a control gate of the MOSFET overlying the first surface and insulated therefrom, the control gate having thereon first and second initial dielectric sidewalls;
• etching an initial cavity in the substrate from the first surface proximate the second sidewall of the gate, wherein etching the initial cavity comprises:
• using the control gate to shadow a part of the first surface proximate the second sidewall;
• implanting at an angle 0<α<90 degrees an amorphizing material into the substrate laterally outside the part of the first surface;
• and
• preferentially etching the initial cavity to an initial depth in a non-amorphized region of the substrate beneath the part of the first surface;
• etching proximate the first sidewall of the gate, a first cavity in the substrate from the first surface to a first depth and having a first portion extending under the control gate at a first depth from the surface;
• etching proximate the second sidewall of the gate, a second cavity in the substrate from the initial cavity to a second depth and having a second portion extending under the control gate toward the first portion at a second depth from the first surface different than the first depth;
• and
• refilling the first and second cavities with semiconductor containing material, wherein at least one of the first and second cavities is refilled with a material having a second lattice constant different than a first lattice constant of the substrate between the first and second cavities, thereby forming source-drain regions of the MOSFET.

A method for forming an insulated gate field effect device, comprising:

• providing a substrate comprising silicon proximate a first surface;
• forming a control gate over the first surface and insulated therefrom;
• etching first and second cavities in the substrate laterally adjacent the control gate, wherein the first cavity has a first portion approximately at a first distance beneath the control gate and the second cavity has a second portion approximately at a second distance beneath the control gate not equal to the first distance, wherein etching the first and second cavities continues until the first and second portions laterally overlap;
• and
• epitaxially re-filling the first and second cavities with a semiconductor material having a different lattice constant than silicon and adapted to induce strain in a part of the substrate between the first and second portions.