Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Communication Breakdown; Workload; Training / Qualification; Situational Awareness; Physiological - Other; Fatigue
Deviation - Altitude Overshoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Environment - Non Weather Related; Human Factors
While on descent in to ZZZ; I the CA was PF.  We received a different runway assignment than anticipated.  We were cleared to 'cross ZZZZZ at 3;000 feet; cleared the ILS [Runway] XXR approach ZZZ.'  The runway change was made in the FMS from YYR to XXR.  While in VNAV path and cleared for the approach we set FAF Glideslope intercept altitude of 2;000 feet in the altitude window.  The last-minute change left us a bit high so we lowered the landing gear and selected LVL CHG in order to re-intercept the path.  ZZZZZ the IF was in the FMS twice and while trying to correct that and heads down and distracted (because we were no longer in VNAV) the aircraft descended through 3;000 feet towards the 2;000 feet set in the ALT window.  I caught the mistake at approximately 2;600 feet MSL and leveled off until intercepting the glide path.  There was no correction from ATC; no known traffic conflict etc.  Normal uneventful landing.  Upon further consideration I determined it was best to file a report.Cause - Short night; last minute runway change; lack of recency of experience...infrequent flying over the last year with the pandemic.PF [should] have better situational awareness and avoid both pilots being heads down even if the PNF is having difficulty correcting the FMS issue.
Air Carrier First Officer reported an altitude deviation during approach caused by possible fatigue; a late runway change and lack of recent flying experience during the pandemic.