Some embodiments include an integrated assembly having a first semiconductor structure containing heavily-doped silicon, a germanium-containing interface material over the first semiconductor structure, and a second semiconductor structure over the germanium-containing interface material. The second semiconductor structure has a heavily-doped lower region adjacent the germanium-containing interface material and has a lightly-doped upper region above the heavily-doped lower region. The lightly-doped upper region and heavily-doped lower region are majority doped to a same dopant type, and join to one another along a boundary region. Some embodiments include an integrated assembly having germanium oxide between a first silicon-containing structure and a second silicon-containing structure. Some embodiments include methods of forming assemblies.