I want to know if I can use the minimum width transistor size set by the tool to design analog circuits?
I have heard about the minimum transistor length, the short channel effects and there is a topic in this forum that discusses this subject, but is there some issues about minimum width? It can be used to minimize area instead of putting more transistors in series to make the relationship W / L too small?
There is nothing wrong with using minimum width. As you mention, it could be used in a long transistor. Just be aware of the tolerances of anything that is "minimum".
usually we use minimum length along the signal path of the circuit if really needs high speed. Except for input diff pair because matching is crucial there.