The Swede was out-scored this year by his teammate Pascal Wehrlein, who has been ousted and looks set to leave F1.
"I had a few nervous weeks but of course it's nice that everything is ready now, especially with Alfa Romeo as a major sponsor and partner," he told the Swedish motoring magazine Teknikens Varld.
"It has been quite a tough career so far in formula one," he said. "It has been difficult to show what I can do with cars that are always at the back of the grid.
"But now with Sauber together with Alfa Romeo, it should mean that for the first time I can be much higher on the grid," Ericsson added.
"Charles Leclerc is an incredibly talented driver who really dominated F2 this year and will of course be a tough opponent for me next season," Ericsson said.
"He is also Ferrari's new super junior but I'm sure we will work well together to develop the car in the best way."
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