The $R+R^2$ model of gravity with the corresponding shallow potential in the
    Einstein frame is consistent with the observations. Recently, many effort have
    been made to generalize the $R+R^2$ (Starobinsky) model of inflation or use
    other shallow potentials to construct a model for the early Universe. We revise
    the question about the shallow potential. We propose a model in which the
    Starobinsky model can emerge through a dynamical mechanism. We show that the
    absence of ghost modes results to constraints on the parameters of the
    Starobinsky model. We obtain the scalar spectral index and the tensor-to-scalar
    ratio of the extended model and study the three-point correlation function of
    the curvature perturbation to estimate the primordial non-Gaussianities of the
    proposed model.

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