I. Introduction
As the size of Si-MOSFETs shrinks down to the nanometer scale, new device technologies such as mobility enhanced channels and multigate architectures are strongly needed to realize advanced CMOS devices. Among them, strained-Si channel engineering, which includes the choices of surface orientations, channel directions, strain configurations, and channel materials are recently becoming more important [1]. Particularly, uniaxial strain can be more effective than biaxial strain in increasing the current drive of short-channel devices, because of the effective mass reduction of holes [2], [3] and even electrons [4]. On the other hand, device structures with new gate configurations are preferred to provide better electrostatic control than the conventional planar structures. Thus, ultrathin-body channels and Si nanowire channels with multigate or gate-all-around structures are highly expected.