The Black & Golds ran in eight tries in a 50-20 win to book a return to rugby HQ in early June.
Cornwall ran riot in the second half scoring five tries to demolish a brave Devon effort.
Ducker, Outlton and Job scored tries in the first half with Honey kicking all three conversions, to a couple of Putt penalties for the hosts.
Despite an early second half score by Watts for Devon, Cornwall kept their foot on the metal with tries from Howe, Tompsett, Speare, Dawe and Peacock with Honey adding another couple of conversions.
Devon had the final say when Avery crashed over but it was too little for the green and whites.
Cornwall will now face Cheshire in the final, after they defeated Durham today and Lancashire lost the Roses match to Yorkshire.
Full report tomorrow