This study presents the fabrication and characterization of a gate-tunable transmon qubit (gatemon) on a planar Germanium (Ge) substrate. The superconductivity in the two-dimensional hole gas is induced by evaporating aluminum atop a thin spacer, separating the superconductor from the Ge quantum well. The Josephson junction is integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. The qubit's tunability is demonstrated over a broad frequency range using resonator and two-tone spectroscopy, with energy relaxation and coherence times up to 75 ns. The results, combined with recent advances in spin qubits, pave the way for novel hybrid and protected qubits in group IV, CMOS-compatible materials. The device's performance is compared with a fixed-frequency reference transmon on a similar substrate, highlighting potential loss mechanisms and areas for improvement. The study also discusses the challenges and future directions for integrating gatemons into spin qubit circuits and superconducting circuits.This study presents the fabrication and characterization of a gate-tunable transmon qubit (gatemon) on a planar Germanium (Ge) substrate. The superconductivity in the two-dimensional hole gas is induced by evaporating aluminum atop a thin spacer, separating the superconductor from the Ge quantum well. The Josephson junction is integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. The qubit's tunability is demonstrated over a broad frequency range using resonator and two-tone spectroscopy, with energy relaxation and coherence times up to 75 ns. The results, combined with recent advances in spin qubits, pave the way for novel hybrid and protected qubits in group IV, CMOS-compatible materials. The device's performance is compared with a fixed-frequency reference transmon on a similar substrate, highlighting potential loss mechanisms and areas for improvement. The study also discusses the challenges and future directions for integrating gatemons into spin qubit circuits and superconducting circuits.