In a food processor, pulse Oreos until fine crumbs form. Transfer to a medium bowl. Add butter and mix to combine.
Pour Oreo mixture into a 9" tart pan. Press into an even layer on bottom and up sides of pan.
Pour caramel over crust and smooth in an even layer. Refrigerate until cold, about 15 minutes.
In a medium heatproof bowl, microwave chips in 30-second increments, stirring between each, until melted and smooth, about 1 minute total. Add Rice Krispies and stir until well coated.
Pour chocolate mixture over caramel and smooth in an even layer. Sprinkle with sea salt. Refrigerate until chocolate is set, at least 2 hours and up to overnight.