The towering Swedish player won a bruising encounter 6-3, 3-6, 5-7, 6-3, 6-3 and on Sunday he will go up against either four-times former winner Rafael Nadal of Spain or Austrian uprise packet Jurgen Melzer for the title.
The match went the full distance with Söderling grabbing the vital break of serve he needed in the seventh game of the deciding set before winning the last two games to make sure.
It will be the second straight year that Söderling has contested the championship match at Roland Garros, losing in the final to Roger Federer last year after handing Nadal his first ever defeat in Paris.
For Berdych it was a disappointing end to a tournament that finally, after years of under-achievement, saw him emerge as a real threat in the Grand Slam events.
"It was really tough to play my game today because he was hitting it so well," Söderling said.
"I felt I was a little bit unlucky in the third set, but he played so well when it realy mattered. I had trouble with his serve.
"When I came here I was just thinking about the first round and seeing what happened and now two weeks later I am in the final again. It's unbelievable."
Two of the tallest men and biggest hitters in tennis, Söderling and Berdych had met eight times previously with the Swede leading the series 5-3. But Berdych won their most recent encounter 6-2, 6-2 en route to the Miami Masters final in April.
As expected, the final four showdown quickly developed into a deadly exchange of big serves and rasping groundstrokes down both flanks on a sun-bathed Philippe Chatrier centre-court.
Berdych was the first to flinch in the sixth game when he double-faulted on break point allowing Söderling to take a 4-2 lead. The Swede comfortably served out to take the set, the first Berdych had lost in the tournament.
It was more of the same in the second set, but this time it was Söderling who let his concentration slip in the fourth game with a couple of loose shots opening the door for the Czech to break serve for the first time.
Berdych held firm in his next three service games to level the set scores at one apiece.
The match was finely poised with the oncourt temperature soaring and it was Berdych who kept the momentum going into the third set, grabbing his second break of serve when Söderling double-faulted at 1-1.
Söderling had an immediate chance to break back in the next game but was denied by a Berdych service winner, but two games later it was Berdych's turn to double fault on break point.
The fifth seed then moved ahead 5-4, but it was Berdych who finished the set stronger rattling off three games in a row as Söderling began to look the more tired of the two big men.
The Swede struggled to hold his serve at the start of the fourth set while Berdych was holding with ease, but it was the Czech who wilted first dropping his serve in the sixth game to leave Söderling 4-2 up.
That pumped up last year's losing finalist and he comfortably served out twice to force a deciding set.