2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/96100A generalization of the Thermo Field Dynamics (TFD) for fermionic degrees of freedom is proposed. Such a generalization follows a previous one where the SU(1,1) thermal group was used to obtain the closed bosonic string at finite temperature. The SU(2) thermal group is introduced to construct a general thermal Bogoliubov transformation to get the type IIB superstring at finite temperature.9 pages, revitex4, minor corrections. Contribution to Fourth International Winter Conference on Mathematical Methods in Physics, 09 - 13 August 2004, Centro Brasileiro de Pesquisas Fisicas (CBPF/MCT), Rio de Janeiro, BrazilHigh Energy Physics - Theorytext