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Boron‐doped diamond layers are grown on freestanding heteroepitaxial diamond substrates by microwave plasma chemical vapor deposition (MPCVD) to verify the high potential of large‐size heteroepitaxial diamond as an ultimate semiconductor material. Due to the high crystallinity and atomically flat surface morphology of the substrate, the MPCVD‐grown boron‐doped diamond layer exhibit excellent surface properties and crystallinity, as measured by X‐ray diffraction and atomic force microscopy. The temperature‐dependent Hall effect measurements are conducted at temperature ranges between 300–800 K with cloverleaf‐shaped van der Pauw geometry. The hole concentration of boron‐doped diamond samples is between 1.1 × 1015 and 5 × 1019 cm−3 at room temperature, and the resistivity is controlled between 10−1 and 20 Ω cm by changing boron to carbon ratio. A specific contact resistance as low as 1.41 × 10−4 Ω cm2 is obtained via annealing at 500 °C. The activation energy of the boron‐doped diamond layers is reduced from 0.35 to 0.12 eV as the amount of boron dopant increases, which is attributed to the formation of impurity band. Finally, the change in the carrier mobility of boron‐doped heteroepitaxial diamond is discussed based on the scattering mechanism.