We describe the leading terms in the asymptotic behavior of the eigenvalues and the eigenfunctions to an elliptic Dirichlet spectral problem in a thin finite cylindrical domain with a periodically oscillating boundary by means of homogenization. Under suitable scaling and structure assumptions, the eigenfunctions show oscillatory behavior, and asymptotically localize with a profile solving a diffusion equation with quadratic potential on the real line. Methods for analysis of spectral asymptotics for heterogeneous media will be briefly discussed.