AbstractA superconducting weak link device using InAs/(AlGa)Sb heterostructure has been fabricated, and its electrical property has been characterized for applications to high‐performance superconducting transistors. the semiconductor layers consist of InAs/(AlGa)Sb heterostructure with high mobility and high electron density; the superconducting electrodes consist of Pb alloy superconducting thin films.InAs/(AlGa)Sb heterostructure was grown by molecular beam epitaxy. the superconducting electrodes were formed by thermal evaporation, and the superconducting weak link device was fabricated using a lift‐off process and wet etching.The film thickness of the InAs quantum well layer was 150 Å, and the thickness of the lead alloy superconducting thin film was 2000 Å. the current density and linear current density at 4.2 K for the device length of 0.3 μm were 3 × 104− 105A/cm2and 4.5 − 15 mA/mm, respectively, and theIcRnproduct was estimated to be ∼2 mV. Therefore, the current density andIcRnproduct in superconducting weak link devices using InAs/(AlGa)Sb heterostructure were estimated to be sufficiently large and its potential for superconducting devices has b