The phase morphology of ultrathin (similar to 15 nm), nonequilibrium films of a symmetrical block copolymer (poly(styrene-bloch-methyl methacrylate) is studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy(XPS). The films were spin-coated from a nonselective solvent onto silicon at room temperature. The film is microphase separated with the microphase stacking in the film plane; i.e., both microphases contact the film surface. Topographically elevated and depressed surface areas consist of polystyrene and poly(methyl methacylate) microphases, respectively. The phase correlation length is in the range of the bulk equilibrium phase correlation length of the system. The poly(methyl methacrylate) phase extends down to the substrate. Reliable phase assignment to topographical features in AFM measurements is possible by topographical contrast enhancement through selective degradation of the poly(methyl methacrylate) microphases in a rf plasma. XPS results on the monomer composition at the film surface confirm the morphological model.