  Inflationary models usually assume the existence of scalar fields or other
exotic gravitational sources. We investigate an alternative approach in which
the entire Universe is considered as a thermodynamic system described by
geometrothermodynamics. A particular van der Waals like fundamental equation is
used to construct an effective inflationary model which is consistent with the
main physical requirements, such as the number of e-foldings and the times for
the onset and end of inflation, predicting in this way a volume of
approximately $10^{-84}$ m$^3$ at the onset of inflation. The phase transition
structure and thermodynamic behavior of the system are consistent with the
expected properties of an inflationary scenario. Cosmological perturbations of
the model are shown to be in agreement with the corresponding primordial power
spectrum providing the seeds for the creation of large-scale structure.
