BIAXIAL STRAINED FIELD EFFECT TRANSISTOR DEVICES

摘要

A process for forming contacts to a field effect transistor provides edge relaxation of a buried stressor layer, inducing strain in an initially relaxed surface semiconductor layer above the buried stressor layer. A process can start with a silicon or silicon-on-insulator substrate with a buried silicon germanium layer having an appropriate thickness and germanium concentration. Other stressor materials can be used. Trenches are etched through a pre-metal dielectric to the contacts of the FET. Etching extends further into the substrate, through the surface silicon layer, through the silicon germanium layer and into the substrate below the silicon germanium layer. The further etch is performed to a depth to allow for sufficient edge relaxation to induce a desired level of longitudinal strain to the surface layer of the FET. Subsequent processing forms contacts extending through the pre-metal dielectric and at least partially into the trenches within the substrate.

主权项

1. A method of manufacturing a semiconductor device, comprising:
providing a substrate having a semiconductor surface layer; forming a field effect transistor on the semiconductor surface layer, the field effect transistor comprising source and drain regions and a gate structure; forming a pre-metal dielectric layer over the field effect transistor; etching openings in the pre-metal dielectric layer and etching to expose contact portions of the substrate on either side of the gate structure; etching, using an orientation-selective wet etch, into the substrate within the openings in the pre-metal dielectric wherein the etching into the substrate proceeds to a sufficient depth so that a buried stressor layer induces longitudinal strain within a semiconductor surface layer through edge relaxation to provide a longitudinally strained active region of the field effect transistor; and forming contacts to the source and drain regions with the contacts formed at least partially within the substrate.