Electrostatic actuator with electrodes having varying distances at different portions

An electrostatic actuator comprising:

• a substrate;
• a first lower electrode and a second lower electrode formed apart from each other above the substrate;
• an electrode portion formed above the first lower electrode and the second lower electrode to have a cavity portion, including a first upper electrode, a second upper electrode, and a third upper electrode formed between the first upper electrode and the second upper electrode, the first upper electrode opposing the first lower electrode and having a first portion and a second portion, a first distance between the first upper electrode and the first lower electrode at the first portion being greater than a second distance between the first upper electrode and the first lower electrode at the second portion, the second upper electrode opposing the second lower electrode and having a third portion and a fourth portion, a third distance between the second upper electrode and the second lower electrode at the third portion being greater than a fourth distance between the second upper electrode and the second lower electrode at the fourth portion, a first boundary portion between the first upper electrode and the third upper electrode having a convex shape, a second boundary portion between the second upper electrode and the third upper electrode having a convex shape, and the electrode portion driving the third upper electrode by applying a potential difference between the first lower electrode and the first upper electrode and between the second lower electrode and the second upper electrode;
• and
• a first layer and a second layer formed in the first boundary portion and the second boundary portion, respectively, wherein
• the first upper electrode and the third upper electrode are spaced apart from each other,
• the second upper electrode and the third upper electrode are spaced apart from each other,
• the first layer is formed between the first upper electrode and the third upper electrode, on an end portion of the first upper electrode, and on an end portion of the third upper electrode, and made of an insulating layer having a compressive stress larger than those of the first upper electrode and the third upper electrode, and
• the second layer is formed between the second upper electrode and the third upper electrode, on an end portion of the second upper electrode, and on an end portion of the third upper electrode, and made of an insulating layer having a compressive stress larger than those of the second upper electrode and the third upper electrode.

An electrostatic actuator comprising:

• a substrate;
• a first lower electrode and a second lower electrode formed apart from each other above the substrate;
• an electrode portion formed above the first lower electrode and the second lower electrode to have a cavity portion, including a first upper electrode, a second upper electrode, and a third upper electrode formed between the first upper electrode and the second upper electrode, the first upper electrode opposing the first lower electrode and having a first portion and a second portion, a first distance between the first upper electrode and the first lower electrode at the first portion being greater than a second distance between the first upper electrode and the first lower electrode at the second portion, the second upper electrode opposing the second lower electrode and having a third portion and a fourth portion, a third distance between the second upper electrode and the second lower electrode at the third portion being greater than a fourth distance between the second upper electrode and the second lower electrode at the fourth portion, a first boundary portion between the first upper electrode and the third upper electrode having a convex shape, a second boundary portion between the second upper electrode and the third upper electrode having a convex shape, and the electrode portion driving the third upper electrode by applying a potential difference between the first lower electrode and the first upper electrode and between the second lower electrode and the second upper electrode;
• and
• a first layer and a second layer formed in the first boundary portion and the second boundary portion, respectively, wherein
• the first upper electrode and the third upper electrode are spaced apart from each other,
• the second upper electrode and the third upper electrode are spaced apart from each other,
• the first layer is formed between the first upper electrode and the third upper electrode, below an end portion of the first upper electrode, and below an end portion of the third upper electrode, and made of an insulating layer having a tensile stress larger than those of the first upper electrode and the third upper electrode, and
• the second layer is formed between the second upper electrode and the third upper electrode, below an end portion of the second upper electrode, and below an end portion of the third upper electrode, and made of an insulating layer having a tensile stress larger than those of the second upper electrode and the third upper electrode.