CPU SMT and layers of mobo?

In a recent news bite here at Tom's (<A HREF="http://www.tomshardware.com/technews/technews-20010828.html#1748" target="_new">First desktop CPU SMT Packaging and New Thermal Barriers</A> ) it talks about surface mount technology (SMT) CPU's, and that SMT would allow for single layer boards.

First, how else is a CPU die attached to the the rest of the chip? What is the internal construction of modern CPUs? What kind of benefits does SMT bring to CPU packaging?

And how does this allow for single layer boards? Current motherboards are 4 or more layers, as far as I know. Was that single layer comment in the news story a typo? Is the motherboard single layer, or is it refering to a board inside the chip package? (Answers to my first set of questions might help to answer this...)

Thanks,
Justin