  We investigate the physical properties, such as star-forming activity, disk
vs. bulge nature, galaxy size, and obscuration of 3796 X-ray selected AGNs at
$0.2<z<0.8$ in the eFEDS field. Using Subaru Hyper Suprime-Cam imaging data in
the $grizy$ bands for SRG/eROSITA-detected AGNs, we measure the structural
parameters for AGN host galaxies by performing a 2D AGN-host image
decomposition. We then conduct spectral energy distribution fitting to derive
stellar mass and rest-frame colors for AGN hosts. We find that (1) AGNs can
contribute significantly to the total optical light down to ${\rm log}\,L_{\rm
X}\sim 42.5\ \rm erg\,s^{-1}$, thus ignoring the AGN component can
significantly bias the structural measurements; (2) AGN hosts are predominately
star-forming galaxies at ${\rm log}\,\mathcal{M}_\star \lesssim 11.3\ M_\odot$;
(3) the bulk of AGNs (64%) reside in galaxies with significant stellar disks,
while their host galaxies become increasingly bulge dominated and quiescent at
${\rm log}\,\mathcal{M}_\star \gtrsim 11.0\ M_\odot$; (4) the size-stellar mass
relation of AGN hosts tends to lie between that of inactive star-forming and
quiescent galaxies, suggesting that the physical mechanism responsible for
building the central stellar density also efficiently fuel the black hole
growth; (5) the hosts of X-ray unobscured AGNs are biased towards face-on
systems and the average $E(B-V)/N_{\rm H}$ is similar to the galactic
dust-to-gas ratio, suggesting that some of the obscuration of the nuclei could
come from galaxy-scale gas and dust, which may partly account for (up to 30%)
the deficiency of star-forming disks as host galaxies for the most massive
AGNs. These results are consistent with a scenario in which the black hole and
galaxy grow in mass while transform in structure and star-forming activity, as
desired to establish the local scaling relations.
