  We develop a theory for two-dimensional diluted magnetic semiconductor
systems (e.g. $\textrm{Ga}_{1-x}\textrm{Mn}_{x}\textrm{As}$ layers) where the
itinerant carriers mediating the ferromagnetic interaction between the impurity
local moments, as well as the local moments themselves, are confined in a
two-dimensional layer. The theory includes exact spatial disorder effects
associated with the random local moment positions within a disordered RKKY
lattice field theory description. We predict the ferromagnetic transition
temperature ($T_{c}$) as well as the nature of the spontaneous magnetization.
The theory includes disorder and finite carrier mean free path effects as well
as the important correction arising from the {\it finite temperature} RKKY
interaction, finding a strong density dependence of $T_{c}$ in contrast to the
simple virtual crystal approximation.
