A method of fabricating a semiconductor device, includes, in part, growing a first layer of oxide on a surface of a first semiconductor substrate, forming a layer of insulating material on the oxide layer, patterning and etching the insulating material and the first oxide layer to form a multitude of oxide-insulator structures and further to expose the surface of the semiconductor substrate, growing a second layer of oxide in the exposed surface of the semiconductor substrate, and removing the second layer of oxide thereby to form a cavity in which a MEMS device is formed. The process of growing oxide in the exposed surface of the cavity and removing this oxide may be repeated until the cavity depth reaches a predefined value. Optionally, a multitude of bump stops is formed in the cavity.