Geometry 1
The geometry can be specified using the built-in tools in COMSOL Multiphysics. First choose to define geometry objects using micrometer units.
1
In the Model Builder tree, under Component 1, click Geometry 1 .
2
In the Settings window for Geometry, locate the Units section. From the “Length unit” list , choose μm.
Rectangle 1
Next create a rectangle to define the geometry extents.
1
In the Model Builder, right click Geometry 1 and choose Rectangle .
2
In the Settings window for Rectangle, locate the “Size and Shape” section. In the Width text field, type 3. In the Height text field, type 0.7.
Polygon 1
Add a polygon that includes points to define the source, drain, and gate contacts. It will also include a line to help create the mesh.
1
Right click Geometry 1 , hover over “More Primitives” to open the submenu and choose Polygon .
2
In the Settings window for Polygon, locate the Object Type section. From the Type list, choose “Closed curve”.
3
Locate the Coordinates section. From the “Data source” list, select Table.
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In the x text field, type 0 0 0.5 0.7 2.3 2.5 3 3.
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In the y text field, type 0.67 0.7 0.7 0.7 0.7 0.7 0.7 0.67.
Polygon 1
1
On the Geometry ribbon/toolbar, click Virtual Operations  and choose Mesh Control Edges .
2
In the Settings window for Mesh Control Edges, locate the Input section. For the “Edges to include:” input panel, select Boundary 4 (the interior line that was just created by the Polygon step). This tells the software that Boundary 4 is used for mesh generation only, and is ignored by the physics settings.
3
Click the Build All button  to build the entire geometry. Use the Zoom Extents button  at the top of the Graphics window to zoom to the full geometry if desired. Notice that the interior line is not shown in the finalized geometry, because it is defined as a Mesh Control Edge in the previous step and will only appear when we set up the mesh later.