Forming a cmos with dual strained channels

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.