The performance and integration density of field-effect transistors (MOSFETs) have been improved by reducing their size. However, in recent years, it has become essential to improve performance by making various innovations to the materials, such as introducing strain into semiconductors to increase mobility through a technique called strain engineering, and increasing the gate capacitance by introducing high-dielectric-constant gate insulating films. The aim of this lecture is to understand the material innovations for improving transistor performance and the expansion of the field of transistor applications through the introduction of new materials.