A superconductor in contact with a normal metal not only induces
superconducting correlations, known as proximity effect, but also modifies the
density of states at some distance from the interface. These modifications can
be resolved experimentally in microstructured systems. We, therefore, study the
local density of states N(E,x) of a superconductor - normal metal
heterostructure. We find a suppression of N(E,x) at small energies, which
persists to large distances. If the normal metal forms a thin layer of
thickness Ln, a minigap in the density of states appears which is of the
order of the Thouless energy ∼ℏD/Ln2. A magnetic field suppresses
the features. We find good agreement with recent experiments of Gu\'eron {\it
et al.}Comment: 5 pages, RevTeX, 7 Figures (included), Submitted to PRB. Revised
version: One figure changed, missprints correcte