  In order to integrate superconducting qubits with rapid-single-flux-quantum
(RSFQ) control circuitry, it is necessary to develop a fabrication process that
fulfills at the same time the requirements of both elements: low critical
current density, very low operating temperature (tens of milliKelvin) and
reduced dissipation on the qubit side; high operation frequency, large
stability margins, low dissipated power on the RSFQ side. For this purpose, VTT
has developed a fabrication process based on Nb trilayer technology, which
allows the on-chip integration of superconducting qubits and RSFQ circuits even
at very low temperature. Here we present the characterization (at 4.2 K) of the
process from the point of view of the Josephson devices and show that they are
suitable to build integrated superconducting qubits.
