  Within the MSSM we propose the chaotic inflationary scenario in which the
inflaton field is a combination of sleptons and the Higgs field states evolving
along the $D$-term flat direction. In the inflation and postinflation reheating
processes, a decisive role is played by the MSSM Yukawa superpotential. The
vacuum energy during the inflationary era is mainly from the muonic Yukawa
coupling, while the inflaton decay and subsequent reheating process dominantly
proceeds due to the strange quark Yukawa term. Because of these, the presented
scenario is predictive and the results obtained agree well with cosmological
observations. In particular, the scalar spectral index and the tensor-to-scalar
ratio are respectively, $n_s\simeq 0.966$ and $r=0.00117$. The reheating
temperature is found to be $T_r\simeq 7.2\times 10^7$ GeV.
