  Tuning the electric properties of crystalline solids is at the heart of
material science and electronics. Generating the electric field-effect via an
external voltage is a clean, continuous and systematic method. Here, utilizing
the unique electric dipole locking in van der Waals (vdW) ferroelectric
alpha-In2Se3, we report a new approach to establish the electric gating effect,
where the electrostatic doping in the out-of-plane direction is induced and
controlled by an in-plane voltage. With the vertical vdW heterostructure of
ultrathin alpha-In2Se3 and MoS2, we validate an in-plane voltage gated coplanar
field-effect transistor (CP-FET) with distinguished and retentive on/off ratio.
Our results demonstrate unprecedented electric control of ferroelectricity,
which paves the way for integrating two-dimensional (2D) ferroelectric into
novel nanoelectronic devices with broad applications.
