You fail to understand companies with their own fabs can DESIGN aswell as optimize for a process THEY control. Same reason Intel says Nehalem will be the first chip to really exploit their 45nm process. Its designed for it. 45nm Core 2 aint.

1. TSMC is the biggest one. But look on their revenue. They have the same revenue as Intel got in 1 single quarter. And having a profit that cant even build 1 45nm factory per year. Yet TSMC produce over 10 times the amount of wafers. TSMC dont make many 45nm chips yet you know. TSMC makes cheap discount chips on a cheap discount process. Thats how their business works and what their consumers want.

2. DRAM is a multitude different business. It makes absolutely no sense what you write. Intel/AMD could make some very expensive very high performance memory in very low quantities. The businessplan would be what? DRAM production lines are simple and extremely cheap in a ultra low profit market.

3. High density leads to low yields? No. Low leakage to low yields? No. I think you mix things up greatly in lack of understanding who they make chips for.

4. So TSMC should use half their profits so AMD can use 5% or less of all their manufactoring lines to make what and for what huge profit? You got even less business knowledge than Hector.

Oh, and remember it would be BULK and not SOI. And AMD would have to respin and redesign large parts of their chips.