Ok I mean thats a question that could easily be answered using google, but I‘ll break it down for you, but keep it simple. Foundries have a multitude of tasks, next to production. They develop and characterize the technology (the actual basic components that companies use to create their designs), they model those components and create packages called PDKs (process development kits) that can be used with industry standard IC design software. They also need to make sure that the technology has a certain yield (meaning they need to tune their entire production processes, from litography, doping, etching, polishing etc) so that the individual components or structures are well within predictable performance. They also need to automate the entire production line as much as possible (in the clean room) to have enough throughput to be economically efficient. Other tasks they need to do are failure analysis (inhouse), measurement and characterization (inhouse), IP developement (sometimes inhouse), repair and maintenance of the equipment (mostly inhouse), customer management. Again very very simplified explanation, but it should be enough for you to understand the basics of a fab operations. More on reddit.com

TSMC has a much, much larger foundry customer base. Until recently Intel was not offering foundry services. Intel's process technology has been behind for the last five or so years, because they got stuck at the 10-7 nm transition. They took a gamble on Cobalt vias and it didn't work out. They also declined to adopt EUV ahead of the 7nm node, believing that quad patterning would be fine. It worked but was not fine. TSMC adopted and scaled EUV earlier and reaped the superior yields earlier. Now Intel are about a half node to a full node behind TSMC, but definitely have far less capacity on that advanced node than TSMC has on theirs. Intel consequently don't have the customer base. There's probably reasons beyond those but those are the ones in the public domain that I know about. Fun fact: TSMC won the highest level of Intel's supplier award this year, because Intel Product are a TSMC customer. More on reddit.com

At this point it's design all the same between Fabless and IDM. The same design tools are used. The same PDK inputs are provided from manufacturing. The design process is largely the same. The fabless company deals with ALL product decisions and distribution. So the marketing, product requirements, etc. are on the fabless company. All the data sheets. All the distribution and sales. All the advertising and branding. The foundry is literally only doing your manufacturing and nothing else. The foundry deals with yield issues and it's selling X units for $Y so the designer doesn't care how that is achieved. That's the foundry's problem because there's a contract price deliverable. The fabless can still need to understand process issues because the SPICE parameters provided are often optimized for generic use but if, for example, you are doing analog in a particular corner of performance, you usually wise to extract your own SPICE models. Foundries are primarily "vanilla digital - @ X MHz clock/Y VDD". If you are doing anything outside of the realm things get a little more complicated to a whole crazy more complicated. Similarly, while you can get basic digital functional test from foundries, the prices aren't always best nor is the bread/depth always what you need for your design (it's vanilla digital test with simple boundary scan), then doing your own production functional test (either yourself or through test houses) can often be necessary (e.g. mixed signal or RF) or financially advantageous. Ditto for packaging - foundries will do packaging but only with standard packages and at a particular price; you can get your product in whole wafers or sawn dice instead. So if you are doing these test/package issues now, there is a role but it may be more of a "project/outsource management" role - you DO need to know how to do things yourself to manage the same job well because you'll also likely be part of the decision process for using the foundry's services vs. DIY vs. 3rd party outsource (test houses, packaging houses). You have to still know these jobs to know what the hell you are managing or deciding! The only advantage IDMs have is they get an extra feedback loop and thus influence on the process design itself. But that's not really so much of a practical reality because of the complexity of the process and its validation which puts a long delay into that feedback loop. There are a lot of disadvantages to IDM: the big one is capital assets you have to carry and the manufacturing R&D. This is a large part of why many companies (like TI) have switch swaths of their product lines to foundry production and shutdown older fabs those products were being manufactured on. Another data point: there have been ZERO IDM fabs funded by Silicon Valley VC since 1990; only fabless have been founded since. Also IDMs like Intel have a lot of "technical debt" in their integrated design-manufacturing process flows. They were all "early stage" players so they had to often invent many of the tools they use to this day. This likely has a major role in Intels failures to effectively enable foundry services using their fabs: you have to have a fair amount of process transparency and standardization to keep your fabless customers happy but Intel didn't do that - I'd bet money on the reason being they can't separate out the interfaces from their legacy proprietary aspects of their MRP systems. We had similar at HP when I was there with ERP/MRP systems. An additional slow process difference is that an IDM can change it production capacity based on plans for a given design. The problem is that still depends on the assumption of market demand which only a company like Intel can safely assume. Fabless deal with this by simply having another foundry available. This is a faster response time option that doesn't require long term commitments until you need capacity. One issue though: if you are a small fry TSMC will generally not have you at 1st priority, for example, so you may have to court UMC or another smaller foundry to meet your product timelines. That can actually be a good thing because company-to-company relations are ALWAYS better when the company size match more closely - the most abusive (sometimes merely accidentally so) relationships happen when there's a large discrepancy. More on reddit.com

Does the US need an American company on its own soil to have manufacturing for a product that is desperately needed in defense? Yes the US needs intel. Frankly they should have subsidized global foundries before they gave up on leading edge nodes so that both TSMC and intel had better competition More on reddit.com