The Saints avenged their only league defeat of the season by beating Rozel Rovers 4-0, with further goals coming from Craig Leitch, his 27th of the season, and Jean-Paul Martyn.
The current Coca-Cola Combination Division I leaders will now face Trinity in the final at Springfield on Saturday 5 April.
Saints manager Craig Culkin said: ‘Fitzy moved into midfield because Liam Walshe is cup-tied and he did a good job; he gave us an extra bit of quality in the area.
‘We dominated the middle through Fitzy, Carl McConnell and Dave Watson while the back three also played very well.
‘The boys have worked hard this season and they thoroughly deserve to be in a final.’
Fitzmaurice scored two fine goals, the first into a top corner from a corner of a penalty area and the second a free kick from outside the penalty area low into a corner.
St Paul’s, two-up at the break, added further goals in the 77th and 78th minutes – Leitch following up his initial shot by rounding the goalkeeper to score from eight yards and then Martyn from a narrow angle as goalkeeper Daniel Gillett fumbled the ball over the goal line.
Rozel assistant manager Gary Westwood said: ‘It was a tough game and we were punished for making a few silly errors.
We matched them in spasms but we did not create as much as we’d of liked in attack.’
Rozel Rovers: Daniel Gillett, Stuart Siddall, Carl Scott, Stuart Truscott, Carl de la Cour, Gareth Wood, Craig Le Sueur, James O’Haire, Anthony McGovern, Andy McCabe, Scott Healey.
Subs used: Paul Roberts, Nick Bolton.
St Paul’s: Andrew Bird; Luke McGlone, Stuart Andre;, James Fortune; Jean-Paul Martyn, Dave Watson, Jon Fitzmaurice, Carl McConnell, Mark Lucas; Craig Leitch, Nathan Taylor.
Subs used: Jamie Cullen, Rupert Murray, Craig Russell.
Officials: Mark Le Cornu, Russell Barry, Ian Solomon.
