  Layered semiconductors, such as MoS2, have attracted interest as channel
materials for post-silicon and beyond-CMOS electronics. Much attention has been
devoted to the monolayer limit, but the monolayer channel is not necessarily
advantageous in terms of the performance of field-effect transistors (FETs).
Therefore, it is important to investigate the characteristics of FETs that have
multilayer channels. Here, we report the staircase-like transfer
characteristics of FETs with exfoliated multilayer MoS2 flakes. Atomic force
microscope characterizations reveal that the presence of thinner terraces at
the edges of the flakes accompanies the staircase-like characteristics. The
anomalous staircase-like characteristics are ascribable to a difference in
threshold-voltage shift by charge transfer from surface adsorbates between the
channel center and the thinner terrace at the edge. This study reveals the
importance of the uniformity of channel thickness.
