Let G be the Q_p-points of a Q_p-split connected reductive group with Borel subgroup P=TN. For any simple root alpha of T in N, we associate functorially to a finitely generated etale (phi,Gamma)-module D over Fontaine's ring (equipped with an additional linear action of the group Ker(alpha)) a G-equivariant sheaf on the flag variety G/P. This functor is faithful. In case of G=GL_2(Q_p) the global sections of this sheaf coincide with the representation D\boxtimes P^1 constructed by Colmez. This is joint work with Peter Schneider and Marie-France Vigneras.