The crystallization behavior, the surface structure, and the nanomechanical properties of a semiconducting polymer play a crucial role in understanding the charge injection process, the transport of the, charge carriers and the processability of the material. Here we study the semi conducting copolymer poly([N,N'-bis (2-octyldodecyl)-11-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl] -alt-5,5'-(2,2'-12 bithiophene)) (P(NDI2OD-T2)) and investigate the influence of annealing conditions on its surface structure through intermittent contact mode atomic force Microscopy (AFM) and AFM-based measurements of amplitude phase distance (APD) curves. For spin-cast thin films as well as for films annealed at temperatures up to 320 degrees C, we find that the edges of crystalline lamellae are exposed at the surface. A 1.2 nm thick layer of indicated by the tip indentation. This suggests that charge injection into P(NDI2OD-T2) films is not hindered by a surface layer of amorphous-material. In 5 nm thick films, corresponding to two monolayers Of P(NDI2OD-T2), after annealing at 320 degrees C, crystalline lamella also orient-perpendicular to the film plane with the (100) surfaces Oriented parallel-to the film plane. The lamellae form 400 nm large areas (terraces) With uniform lamella height. The step height between adjacent terraces is 2.2 nm, and we attribute it to monomoleculat steps between the molecular thin layers of edge-on-oriented polymer chains. This well-defined molecular conformation at the film surface with the chain backbone and the pi-stacking direction oriented in the film plane is presumably an important factor contributing to the exceptional performance of P(NDI2OD-T2) in bottom-gate organic field-effect transistors.