Davide Frattesi hit a 99th minute extra time winner to send Inter in total to the last 7-6.
Sommer, excellent at night, said afterwards: “It was a crazy game. I am really proud of this team and how we played.
“We were already a bit out and then we came back – great.
“It means a lot – you don't have many opportunities to go to a final. We knew it was extra time in the last four minutes that it was our last chance to continue.
“We put everything on this field with the fans together.”