HIGH MOBILITY FIELD EFFECT TRANSISTORS WITH A RETROGRADED SEMICONDUCTOR SOURCE/DRAIN

摘要

Monolithic FETs including a channel region of a first semiconductor material disposed over a substrate. While a mask, such as a gate stack or sacrificial gate stack, is covering the channel region, an impurity-doped compositionally graded semiconductor is grown, for example on at least a drain end of the channel region to introduce a carrier-blocking conduction band offset and/or a wider band gap within the drain region of the transistor. In some embodiments, the compositional grade induces a carrier-blocking band offset of at least 0.25 eV. The wider band gap and/or band offset contributes to a reduced gate induced drain leakage (GIDL). The impurity-doped semiconductor may be compositionally graded back down from the retrograded composition to a suitably narrow band gap material providing good ohmic contact. In some embodiments, the impurity-doped compositionally graded semiconductor growth is integrated into a gate-last, source/drain regrowth finFET fabrication process.