  We have integrated single and coupled superconducting transmon qubits into
flip-chip modules. Each module consists of two chips -- one quantum chip and
one control chip -- that are bump-bonded together. We demonstrate time-averaged
coherence times exceeding $90\,\mu s$, single-qubit gate fidelities exceeding
$99.9\%$, and two-qubit gate fidelities above $98.6\%$. We also present device
design methods and discuss the sensitivity of device parameters to variation in
interchip spacing. Notably, the additional flip-chip fabrication steps do not
degrade the qubit performance compared to our baseline state-of-the-art in
single-chip, planar circuits. This integration technique can be extended to the
realisation of quantum processors accommodating hundreds of qubits in one
module as it offers adequate input/output wiring access to all qubits and
couplers.
