First of all, of course, we must understand the basic working principle, parameters and so on of transistors.

Then you should be familiar with the manufacturing process of IC, such as silicon wafer manufacturing, oxidation, deposition, lithography, etching and glue removal.

Then you should be familiar with various manufacturing processes, including bipolar, CMOS, BICMOS, gallium arsenide and so on.

You also need to know all kinds of electromagnetic and electrical knowledge, ESD, packaging and so on.

Of course, there are EDA tools and various layout design skills.

Finally, of course, the layout designer must also know the necessary circuit design knowledge, and need to know which places play a decisive role in the performance of the circuit system.

I didn't scare you. There are many more. Typesetting is a tiring job