It depends on what kind of grass.
I made Bermuda grass go away for 12 to 15 years (it might still be gone, but we don't live at that house anymore) by sifting the roots out of the dirt with a 1/2-inch-gauge hardware cloth screen over the wheelbarrow. The dirt that fell through went back into the yard; the root segments went away.
And I could plant immediately. That yard was so situated that I planted roses, some bulbs, and zucchini; none of them were molested by Bermuda grass!
You might also smother the grass by solarizing it: use sheets of black plastic, weight them down with bricks or similar, and leave the plastic on for several nice, hot weeks. The grass will die. Then you can use Lasagna Gardening techniques or build raised beds over it and have fun!
No -cides needed.
Sunset Zone 17, USDA Zone 9