[mih]

Intel, Samsung - They design chips as well as fabricate them. Design starts from a very high level specification down to individual transistors.

Fabs such as TSMC, Global Foundries etc.: They manufacture chips in addition to specifying the rules to be followed when laying out the logical design (circuits) on silicon. Rules differ by the given node (7nm, 10nm, 14nm etc.) and specify things such as the width of a gate, thickness of a metal wire on the chip, spacing and tolerances etc. The actual number just indicates technology advancement. 7nm means the manufacturing process is more advanced than the 10nm process and has little to do with physical reality. Hence Intel's 10nm process might not be the same as TSMC's 10nm. While Intel can in principle adhere to TSMC's 7nm process, they already have their own R&D and develop their process in-house. Switching to a different foundry's node would involve redoing a number of steps before the chip can be manufactured. Besides, fabs guard their process jealously and are very protective of their IP.

Design companies such as AMD, Qualcomm, Broadcom etc. just design the circuits and adhere to the specification of their chosen fab and node to layout the design on silicon.

Source: I worked in the EDA[1] industry.

[1] https://en.wikipedia.org/wiki/Electronic_design_automation