  Twisted bilayer graphene provides a new two-dimensional platform for studying
electron interaction phenomena and flat band properties such as correlated
insulator transition, superconductivity and ferromagnetism at certain magic
angles. Here, we present strong evidence of correlated insulator states and
superconductivity signatures in p-type twisted double-bilayer WSe$_2$. Enhanced
interlayer interactions are observed when the twist angle decreases to a few
degrees as reflected by the high-order satellites in the electron diffraction
patterns taken from the 2H/3R-stacked domains reconstructed from a conventional
Moir\'e superlattice. In contrast to twisted bilayer graphene, there is no
specific magic angle for twisted WSe$_2$. The flat band properties are observed
at twist angles ranging from 1 to 4 degrees. The highest superconducting
transition temperature observed by transport measurement is 6 K. Our work has
facilitated future study in the area of flat band related properties in twisted
transition metal dichalcogenide layered structures.
