Performance comparison of ultrathin fully depleted silicon-on-insulator inversion-, intrinsic-, and accumulation-mode metal-oxide-semiconductor field-effect transistors

This work demonstrates the performance comparison of ultrathin fully depleted (FD) silicon on insulator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs) with various structures. The current drivability and immunity to the short channel effect are analyzed for FD-SOI n-channel MOSFETs (nMOSFETs) with various SOI layer thickness and SOI layer dopant concentrations based on the device simulation study. The SOI layer dopant concentrations are widely varied from conventional inversion-mode MOSFET, undoped-mode (intrinsic-mode) to the accumulation-mode MOSFET, where the accumulation-mode MOSFETs has the same dopant type in SOI layer as those of the source and the drain regions. The results suggest that the short channel effect immunity becomes comparable among various SOI layer dopant concentrations when SOI layer thickness is less than 10 nm. The current drivability is higher in the order of accumulation-, intrinsic-, and inversion-mode MOSFETs, and the mechanism of the current drivability increase is explained. In addition, accumulation-mode MOSFETs with polycrystalline silicon (poly-Si) gate electrode can maintain their high current drivability even for short channel generation because the gate capacitance decrease due to the poly-Si depletion effect does not arise. Thus, accumulation-mode MOSFETs can maximize the performance of the ultrathin FD-SOI MOSFETs.