Spain will face two-time defending champions Italy for the Davis Cup title after beating Germany in a deciding doubles match to reach the final for the first time in six years.
Pablo Carreno Busta gave Spain an early lead with victory over Jan-Lennard Struff in the opening singles match.
But German world number three Alexander Zverev battled past Jaume Munar to send the tie to a decider.
Marcel Granollers and Pedro Martinez, called upon to settle their nation's quarter-final against the Czech Republic on Thursday, delivered once again to beat Kevin Krawietz and Tim Puetz 6-2 3-6 6-3.