  Transition-metal dichalcogenides (TMDs) $MX_2$ ($M$ = Ti, Nb, Ta; $X$ = S,
Se, Te) exhibit a rich set of charge density wave (CDW) orders, which usually
coexist and/or compete with superconductivity. The mechanisms of CDWs and
superconductivity in TMDs are still under debate. Here we perform an
investigation on a typical TMD system, 1\emph{T}-TaSe$_{2-x}$Te$_x$ ($0 \leq x
\leq 2$). Doping-induced disordered distribution of Se/Te suppresses CDWs in
1\emph{T}-TaSe$_2$. A domelike superconducting phase with the maximum
$T_\textrm{c}^{\textrm{onset}}$ of 2.5 K was observed near CDWs. The
superconducting volume is very small inside the CDW phase and becomes very
large instantly when the CDW phase is fully suppressed. The observations can be
understood based on the strong \emph{\textbf{q}}-dependent electron-phonon
coupling-induced periodic-lattice-distortion (PLD) mechanism of CDWs. The
volume variation of superconductivity implies the emergence of domain walls in
the suppressing process of CDWs. Our concluded scenario makes a fundamental
understanding about CDWs and related superconductivity in TMDs.
