Lead inductance comes from the internal bond wires of the FET and is typically around 1nH per mm. If the device has leads, such as in a TO-247 package, these external connections also add to L.If switching times are measured in microseconds, the amperes of switching current only produce millivolt transients, and the gate drive voltage changes very little.

However, wide bandgap (WBG) devices can switch tens of amps in a few nanoseconds, generating transients of about 2-5V per nH of connection inductance. If this transient is added to the gate drive, the MOSFET will stop switching off, and there is even a risk of ringing or device failure. To combat these parasitic inductances, 4pin devices exist.

Related article; Why 4-pin devices are important in SiC TO-247 packages 2021.01.28