Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs.
Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. For example, three-dimensional transistors such as a Fin Field-Effect Transistors (FinFETs) have been introduced to replace planar transistors. Although existing FinFET devices and methods of fabricating FinFET devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. For example, the FinFETs for different circuits such as core (logic) circuits and Static Random Access Memory (SRAM) circuits may have different designs, and the source/drain epitaxy regions grown from neighboring fins may need to be merged for some circuits (such as logic circuits), and need to be separated from each other for other circuits (such as SRAM circuits). However, to save manufacturing cost, the epitaxy for different regions is performed simultaneously. This causes difficulty for selectively making epitaxy regions merged for some circuits, and not merged for other circuits. Accordingly, the merged epitaxy regions need to be trimmed to separate the merged epitaxy regions from each other.