  In this paper, we present the construction of tensor network states (TNS) for
some of the degenerate ground states of 3D stabilizer codes. We then use the
TNS formalism to obtain the entanglement spectrum and entropy of these
ground-states for some special cuts. In particular, we work out the examples of
the 3D toric code, the X-cube model and the Haah code. The latter two models
belong to the category of "fracton" models proposed recently, while the first
one belongs to the conventional topological phases. We mention the cases for
which the entanglement entropy and spectrum can be calculated exactly: for
these, the constructed TNS is the singular value decomposition (SVD) of the
ground states with respect to particular entanglement cuts. Apart from the area
law, the entanglement entropies also have constant and linear corrections for
the fracton models, while the entanglement entropies for the toric code models
only have constant corrections. For the cuts we consider, the entanglement
spectra of these three models are completely flat. We also conjecture that the
negative linear correction to the area law is a signature of extensive ground
state degeneracy. Moreover, the transfer matrices of these TNS can be
constructed. We show that the transfer matrices are projectors whose
eigenvalues are either 1 or 0. The number of nonzero eigenvalues is tightly
related to the ground state degeneracy.
