Please, provide a summary of advantages and disadvantages of a transistor layout with multiple fingers (MF) vs single finger?
When laying out a MOSFET with a particular width and length, in an EDA tool, one has two options with regards to the shape of the gate:
1) Single stripe (classical case) (one finger);
2) Several stripes (several fingers).
Hypotheses (based on various Internet forums):
1) MF provide more flexibility in layout planning for transistor with high W/L or L/W. In other words, allows making a layout more square-like.
2) MF allow better matching of transistors, when needed. For example, if using common-centroid techniques.
3) MF layout reduces gate resistance (for AC). If so, can you explain why?
4) MF reduce current density in the gate if there are technology limitations on this.
Can someone with knowledge do a comparison of the two approaches?
Figure 1: One finger.
Figure 2: Two fingers. Two transistors in parallel (widths are summed).
Figure 3: Two fingers. Two transistors in series (lenghts are summed).