Like I said semantics. For clarity sake I'll use the term uncaused Being.
A cause is always ontologically prior to its effect, and one can not be prior to himself. God is not an effect and therefore does not need a cause.
The assumption is as Sarte believed "everthing is caused." An effect is what is being actualized, and a cause is what is actualizing. And God is certainly not self-caused.
Theist don't believe that everthing has to have a cause - believing that everthing has a cause does not help the atheist either. Infinite regression against the "science" of Big Bang theory.
A Uncaused Being does not need a cause, He exist by His very nature.
God has not revealed the total extent of that nature so I cant answer what is God composed of - I dont think He is a composite of seperate things. We know from revelation that He is Eternal and Creator. Beyond revelation there is no way to ascertain the totality of Gods natue.
God is a Uncaused Being who causes things to be actualized, but He Himself is not actualized and hence not an effect - therefore the term Uncaused Cause (although admitadly not a good choice of words for semanticaly picky people).
Now if you have a problem with the term as being impossible. I would simly ask "How do you know that?" (Wittgenstein is appropriate here) Language games.
Either somthing comes from noting or somthing always was. You may assert that all contigent parts of the universe are equal to the whole and therfore the whole is also contingent. This is the fallacy of composition. Or you may claim that the universe is more than all the parts; the parts are caused or dependent but the whole is not caused it is simply there as Bertrand Russell said. But once you admit that ther is an eternal uncaused somthing which is more than all the finite parts and upon which they are dependent then you have acknowledged what the theist argued all along - God.
I give credit for some of these thoughts to Norman Geisler.
For your reading pleasure.
http://www.reasonablefaith.org/site/PageServer?pagename=q...