Applying transmission Kikuchi diffraction (TKD) allows us to fundamentally investigate the Si-doped-hafnium-oxide (HSO) microstructure that results from the interface layer present in ferroelectric field-effect transistors. In addition to the predominant orthorhombic phase, dendritic HSO grains larger than 100 nm govern the microstructure composition. Furthermore, the observed strong out-of-plane texture aligned along the [110] and [011] axis clearly differs from features found in hafnium oxide thin films grown on TiN layers. Our TKD analysis shows that the texture intensity strongly varies for samples annealed at different temperatures. Additionally, intra-granular misorientation and chemical composition analyses of the layers provide insight into the crystallization process of these ferroelectric thin films.