There are many different types of trusts that can be created. However, most require some level of tradeoff between estate tax minimization and access to the trust assets. A spousal lifetime access trust (SLAT) can offer the best of both worlds, according to the Wills, Trusts & Estates Prof Blog in "Exploring the Spousal Lifetime Access Trust."
A SLAT is an irrevocable trust that one spouse, the settlor-spouse, creates for the benefit of the other spouse, the beneficiary-spouse. Through use of the gift tax exemption, the beneficiary-spouse can access trust assets including income, during his or her lifetime. The settlor-spouse might then have access to funds through the beneficiary-spouse. Children of the beneficiary-spouse can also be named as beneficiaries.
There are potential drawbacks for the settlor-spouse with a SLAT. If the couple gets divorced, the settlor-spouse will likely lose access to trust assets. The same thing can happen, if the beneficiary-spouse passes away first, depending on other estate planning decisions that were made.
An estate planning attorney can advise you on creating an estate plan that fits your unique circumstances and could include a SLAT.
Reference: Wills, Trusts & Estates Prof Blog (April 16, 2018) "Exploring the Spousal Lifetime Access Trust."