Stressed MOS devices and methods for their fabrication are provided. The
stressed MOS device comprises a T-shaped gate electrode formed of a
material having a first Young's modulus. The T-shaped gate electrode
includes a first vertical portion and a second horizontal portion. The
vertical portion overlies a channel region in an underlying substrate and
has a first width; the horizontal portion has a second greater width. A
tensile stressed film is formed overlying the second horizontal portion,
and a material having a second Young's modulus less than the first
Young's modulus fills the space below the second horizontal portion. The
tensile stressed film imparts a stress on the horizontal portion of the
gate electrode and this stress is transmitted through the vertical
portion to the channel of the device. The stress imparted to the channel
is amplified by the ratio of the second width to the first width.