How can I add attributes to craft field? In my template I have this,

{{ 
    craft.fields
    .getFieldByHandle('ethnicOrigin')
    .getFieldType()
    .getInputHtml( 'fields[ethnicOrigin]', '') | raw
}}


which returns me a &lt;select&gt; html element Is it possible to add specific class to this select and or data- attribute?
If you take a look at the FieldType documentation it looks as the you need to create a template for the input field in which you can specify the actual html for your field. The example in the documentation is for a textarea but in your case you can substitute this for a select. 

Then once you've done that just override the getInputHtml method to render your new template.