  The control of a superconducting current via the application of a gate
voltage has been recently demonstrated in a variety of superconducting devices.
Although the mechanism underlying this gate-controlled supercurrent (GCS)
effect remains under debate, the GCS effect has raised great interest for the
development of the superconducting equivalent of conventional metaloxide
semiconductor electronics. To date, however, the GCS effect has been mostly
observed in superconducting devices made by additive patterning. Here, we show
that devices made by subtractive patterning show a systematic absence of the
GCS effect. Doing a microstructural analysis of these devices and comparing
them to devices made by additive patterning, where we observe a GCS, we
identify some material and physical parameters that are crucial for the
observation of a GCS. We also show that some of the mechanisms proposed to
explain the origin of the GCS effect are not universally relevant.
