Selective epitaxial growth (SEG) of thin SiGe films through small windows on an oxide covered silicon substrate has been investigated with the aim of forming high-quality relaxed SiGe without growing thick films. Atomic force microscope images show that the surface of SiGe films are flat in small windows but that the centers of films are caved in large windows. The caving of SiGe films is larger than that of Si films of the same thickness, reflecting the influence of strain. The flat-caved transition is observed to occur at a smaller window size with decreasing growth temperature. The SiGe thin films are preliminary used to fabricate a neighboring confinement structure (NCS) which requires relaxed SiGe and a NCS PL spectrum is demonstrated.