Complementary field effect transistors having strained superlattice structure

Claim 1

A complementary field effect transistor device comprising a substrate and a plurality of epitaxial semiconductor layers grown thereon, an n-channel field effect transistor formed in a first epitaxial layer having n-type source and drain regions and a channel region, and a p-channel field effect transistor formed in a second epitaxial layer and having p-type source and drain regions and a channel region, said second epitaxial layer including a strained germanium-silicon alloy layer in the channel region. said p-channel field effect transistor being formed in a first isolated region of said second epitaxial layer and having a channel region composed of a lower layer of strained germanium-silicon alloy and an unstrained silicon layer formed on said strained germanium-silicon alloy, and said n-channel field effect transistor being formed in a second isolated region of said first epitaxial layer and having a channel region including an unstrained germanium-silicon alloy layer, a silicon layer formed on said unstrained germanium-silicon layer, and a strained germanium-silicon alloy layer formed on said silicon layer, and whereby the carrier mobilities in the channel regions of the n-channel and p-channel field effect transistors are comparable.