Patent ID: 7405099

Claim:
A method of forming a high-aspect ratio microelectromechanical (MEM) device on a substrate including a substrate layer, an active layer, and a first sacrificial layer disposed at least partially therebetween, the method comprising the steps of: forming a first trench, a second trench, and a third trench in the active layer, each trench having an opening and sidewalls defining substantially equal first trench widths; forming a second sacrificial layer over a surface of the active layer and the sidewalls of each of the trenches; forming a third sacrificial layer over the second sacrificial layer and sealing the openings of each of the trenches with the third sacrificial layer; forming an etch hole in the second sacrificial layer and the third sacrificial layer between the first trench and the second trench to expose a portion of the active layer; removing material from the active layer between the first trench and the second trench to form a cavity having sidewalls and an opening; forming a fourth sacrificial layer over the third sacrificial layer and the sidewalls of the cavity and sealing the cavity and its opening with the fourth sacrificial layer; and removing the second sacrificial layer, the third sacrificial layer, and the fourth sacrificial layer to expose the third trench and form a fourth trench in the active layer from the first and the second trench, the fourth trench having sidewalls defining a second trench width that is greater than the first trench width.