Forming a CMOS with dual strained channels

摘要

The present invention relates generally to a semiconductor device, and more particularly, to a structure and method of forming a compressive strained layer and a tensile strained layer on the same wafer. A lower epitaxial layer may be formed adjacent to a tensile strained layer. An upper epitaxial layer may be formed over a portion of the lower epitaxial layer. Thermal oxidation may convert the upper epitaxial layer to an upper oxide layer, and thermal condensation may causes a portion of the lower epitaxial layer to become a compressive strained layer. The upper oxide layer and a remaining portion of the lower epitaxial layer may be removed, leaving the tensile strained layer and the compressive strained layer.

主权项

1. A method comprising:
forming a first hardmask on a tensile strained semiconductor layer; removing a portion of the first hardmask to form an opening, the opening exposing an upper surface of the tensile strained semiconductor layer; removing a portion of the tensile strained semiconductor layer, selective to the first hardmask, down to a buried insulator layer, to form an undercut opening that it extends laterally beneath the first hardmask; forming a first epitaxial layer in the undercut opening adjacent to and contacting a sidewall of the tensile strained layer; forming a second epitaxial layer in the undercut opening adjacent to and contacting a sidewall of the first epitaxial layer; forming a third epitaxial layer in the undercut opening adjacent to and contacting the second epitaxial layer; removing the first hardmask; forming a second hardmask on an upper surface of the tensile strained semiconductor layer, an upper surface of the first epitaxial layer, an upper surface of the second epitaxial layer, and only a portion of an upper surface of the third epitaxial layer; forming an upper epitaxial layer on an exposed portion of the upper surface of the third epitaxial layer; and performing a thermal oxidation process, such that the upper epitaxial layer is converted to an upper oxide layer and thermal condensation causes a portion of the epitaxial layer below to become a compressive strained layer.