II. MOSFET DEVICE OVERVIEW
Before we go further, we first overview the principle structure and important parameters of the core unit of CMOS i.e.
MOSFETs. It will give us firm understanding of the scaling problems. The name 'metal-oxide-semiconductor' represents
the materials used to form the early fabricated MOSFETs. Figure 1 shows the typical structure of a MOSFET with
the three material layers: the metal gate electrode, the gate dielectric, and the silicon substrate. Nowadays, the metal gate
electrode and silicon oxide-based gate dielectric have been replaced by polycrystalline silicon and high-k material such
as Hf-based Zr-based, respectively [6]. The source and drain are formed by adding impurity dopant
into substrate. The semiconductor material in the source and