Foster's side have been drawn against Hampshire in the semi-final on August 14 and the wicketkeeper says his side will go in to the finals day at the Rose Bowl full of confidence and buoyed by Tuesday night's dramatic victory.
"I'm absolutely buzzing, thrilled it was a tremendous chase. I think that win is going to give us some serious belief," he said.
"We are in the semi-finals, we were second in our group, we won today against a top Lancashire unit so yeah course we can believe.
"Ultimately now the semi-final is the most important game for us and we have got to get past Hampshire, we have got a lot of confidence against them we beat them twice in the group stages but it's all on the day and who is going to take the pressure the best and who is going to execute their skills and hopefully it will be us."
Foster also says the team has learned from the disappointment of losing at the semi-finals stage in 2008, adding: "There are a few things we have picked up from that experience.
"Ultimately we are playing some great cricket and we believe we are going to go there with a lot of confidence."
Matt Walker and Mark Pettini were the heroes for Essex, posting the highest t20 partnership in the competition this season, and now Walker, 36, can't wait for finals day.
"Bring it on," he said.
"I have been fortunate enough to win it (with Kent in 2007) and it's something you don't want to go and lose, you don't go for the day out you go to win. If you win it it's the best day of your life – who knows? Maybe."
"If I'm honest I didn't expect to feature much in the Twenty20 campaign this year, mainly because of all the overseas players that you have coming in to the game, great players, big hitters but as it's turned out there have been a few injuries and there's something to be said for a bit of experience in the ranks too.
"It just goes to show you're never too old."
For his part Pettini is glad to have hit form again with the bat and is clearly feeling liberated after giving up the captaincy.
"You only play in a certain amount of big games in your career and you have got to enjoy them and hope you do well in them," he said.
"I had a great partnership with Matty tonight and we really enjoy batting together and it was nice to get us over the line.
"It was obviously really important being a quarter-final so I'm very happy, playing in front of a full house it doesn't really get much better."
Turn to Page 79 for full report.