The 23-year-old beat the German third seed 6-4 2-6 6-4 to become the first British man aside from Andy Murray to reach an ATP semi-final since James Ward at Queen’s back in 2011.
Evans will play top seed Tommy Haas for a place in the final on Saturday, while Marin Cilic faces Bjorn Phau in the other last-four clash.
The Briton can can expect to rise from 147 to around 124 in the world rankings on Monday thanks to his impressive run.
Evans reached the third round of the US Open last year, losing to Tommy Robredo in four sets.
MORE: The latest football news
MORE: The latest tennis news