Disclosed are embodiments of a hybrid-orientation technology (HOT) wafer and a method of forming the HOT wafer with improved shallow trench isolation (STI) structures for patterning devices in both silicon-on-insulator (SOI) regions, having a first crystallographic orientation, and bulk regions, having a second crystallographic orientation. The improved STI structures are formed using a non-selective etch process to ensure that all of the STI structures and, particularly, the STI structures at the SOI-bulk interfaces, each extend to the semiconductor substrate and have an essentially homogeneous (i.e., single material) and planar (i.e., divot-free) bottom surface that is approximately parallel to the top surface of the substrate. Optionally, an additional selective etch process can be used to extend the STI structures a predetermined depth into the substrate.