NL25 oop w/ flopped trips, what do I do here?

[seatown]

About 20 hands in w/ villian, haven't seen anything out of line. He's been raising pf the last few orbits but haven't went to sd yet. As played, do I have to call this river or did i leave myself room to fold? I was wondering if AcKc makes this type of move?

PokerStars No-Limit Hold'em, $0.25 BB (5 handed) Converter Tool from (Format: Bet The Pot)

MP ($47.60)
Button ($29.35)
SB ($5.90)
BB ($44.05)
Hero ($66)

Preflop: Hero is UTG with , .
Hero calls $0.25, 1 fold, Button raises to $1.25, 2 folds, Hero calls $1.

Flop: ($2.85) , , (2 players)
Hero checks, Button bets $2.25, Hero calls $2.25.

Turn: ($7.35) (2 players)
Hero checks, Button bets $5.5, Hero calls $5.50.

River: ($18.35) (2 players)
Hero checks, Button bets $20.35 (All-In), Hero folds.

Final Pot: $-2

[Starkes]

[k3nt]