We investigated electronic structures and carrier transport properties through a single Ge quantum dot (QD) and double QDs (DQDs) devices using the effective-mass model in combination with the non-equilibrium Green's function technique. Effects of Ge QD diameters and coupling-barrier width/height of Si-containing layers on the Coulomb stability and charge stability diagrams of Ge single-hole transistors and DQDs, respectively, were numerically analyzed. Optimal structure design of Ge DQDs and SHTs for charge stability and sensing is proposed.