A search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton-proton collisions at $\sqrt{s}$ = 8 TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5 inverse-femtobarns. The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark mass eigenstate stop_2 decaying to a lighter top-squark mass eigenstate stop_1 via either stop_2 $\to$ H stop_1 or stop_2 $\to$ Z stop_1, followed in both cases by stop_1 $\to$ top neutralino, where the neutralino is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the stop_2 and stop_1 states is approximately equal to the top-quark mass, m_(stop_2) - m_(stop_1) ~ m_(top), which is not probed by searches for direct stop_1 squark pair production. The analysis excludes top squarks with masses m(stop_2) less than 575 GeV and m(stop_1) less than 400 GeV at a 95% confidence level.

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