Improved Electrical Characteristics of Ge pMOSFETs With ZrO2/HfO2 Stack Gate Dielectric

Electrical characteristics of Ge pMOSFETs with HfO
₂
, ZrO
₂
, ZrO
₂
/HfO
₂
, and HfZrO
_x
gate dielectrics are studied in this letter. A lower equivalent oxide thickness (EOT) is obtained in ZrO
²
device, which, however, has a higher interface trap density (D
_it
) due to its inferior dielectric/Ge interface. Interestingly, the Dit and sub-threshold swing of Ge pMOSFETs are clearly reduced by ZrO
₂
/HfO
₂
stack gate dielectric. A peak hole mobility of 335 cm
²
/V-s is achieved in ZrO
₂
/HfO
₂
device thanks to good dielectric/Ge interface. Furthermore, the EOT of ZrO
₂
/HfO
₂
device is 0.62 nm, and the leakage current is 2 × 10
^-3
A/cm
²
. Therefore, a ZrO
₂
/HfO
₂
stack gate dielectric is promising for Ge MOSFETs.