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We present existence, uniqueness, and sharp regularity results of solution  to the stochastic partial differential equation (SPDE)  \begin{align}  \label{abs eqn}  du=(a^{ij}(\omega,t)u_{x^ix^j}+f)dt +(\sigma^{ik}(\omega,t)u_{x^i}+g^k)dw^k_t, \quad u(0,x)=u_0,  \end{align}  where $\{w^k_t:k=1,2,\cdots\}$ is a sequence of independent Brownian motions.The coefficients are merely measurable in $(\omega,t)$ and can be unbounded andfully degenerate, that is, coefficients $a^{ij}$, $\sigma^{ik}$ merely satisfy  \begin{align}  \label{abs only} \left(\alpha^{ij}(\omega,t)\right)_{d\times d}:=\left(a^{ij}(\omega,t)-\frac{1}{2}\sum_{k=1}^{\infty}\sigma^{ik}(\omega,t)\sigma^{jk}(\omega,t)\right) \geq 0.  \end{align} In this article, we prove that there exists a unique solution $u$to \eqref{abs eqn}, and \begin{align}  \notag \|u_{xx}\|_{\mathbb{H}^\gamma_p(\tau,\delta)} &\leq N(d,p) \bigg(\|u_0\|_{\mathbb{B}_p^{\gamma+2 \left(1-1/ p \right)}} + \|f\|_{\mathbb{H}^\gamma_p( \tau,\delta^{1-p} )}  \label{abs est} &\qquad \qquad+\|g_x\|^p_{\mathbb{H}^\gamma_p( \tau,|\sigma|^p \delta^{1-p},l_2)}+ \| g_x\|_{\mathbb{H}^\gamma_p(\tau,\delta^{1-p/2},l_2)} \bigg), \end{align} where $p\geq 2$, $\gamma\in\mathbf{R}$, $\tau$ is an arbitrary stopping time, $\delta(\omega, t)$ is thesmallest eigenvalue of $\alpha^{ij}(\omega, t)$, $\mathbb{H}_p^\gamma(\tau,\delta)$ is a weighted stochastic Sobolev space, and $\mathbb{B}_p^{\gamma+2\left(1-1/ p \right)}$ is a stochastic Besov space.

A sharp $L_p$-regularity result for second-order stochastic partial differential equations with unbounded and fully degenerate leading coefficients