  SPHERE+ is a proposed upgrade of the SPHERE instrument at the VLT, which is
intended to boost the current performances of detection and characterization
for exoplanets and disks. SPHERE+ will also serve as a demonstrator for the
future planet finder (PCS) of the European ELT. The main science drivers for
SPHERE+ are 1/ to access the bulk of the young giant planet population down to
the snow line ($3-10$ au), to bridge the gap with complementary techniques
(radial velocity, astrometry); 2/ to observe fainter and redder targets in the
youngest ($1-10$\,Myr) associations compared to those observed with SPHERE to
directly study the formation of giant planets in their birth environment; 3/ to
improve the level of characterization of exoplanetary atmospheres by increasing
the spectral resolution in order to break degeneracies in giant planet
atmosphere models. Achieving these objectives requires to increase the
bandwidth of the xAO system (from $\sim$1 to 3\,kHz) as well as the sensitivity
in the infrared (2 to 3\,mag). These features will be brought by a second stage
AO system optimized in the infrared with a pyramid wavefront sensor. As a new
science instrument, a medium resolution integral field spectrograph will
provide a spectral resolution from 1000 to 5000 in the J and H bands. This
paper gives an overview of the science drivers, requirements and key
instrumental trade-off that were done for SPHERE+ to reach the final selected
baseline concept.
