In this work, a new model based on energy balance for heteroepitaxial growth on a patterned substrate and an additional thin buffer layer on top of it has been developed. The structure used in our model is assumed to be GeSi/buffer-Si/patterned-Si and comparisons are made with simple crystalline GeSi/Si. However, the model described here is quite general and can be adopted for any other material systems. Using this model, coupled with experimentally known material constants, the critical layer thickness (hc ) of a lattice mismatched heterolayer can be determined for a patterned substrate, having a characteristic “seed pads” size (l), and a buffer layer thickness (hb ). The dislocation-free condition under this case is also established.