More specifically with html5 form elemnts and html5 shiv

there are many html5 tags which are not supportes in IE<9 browsers . html5shiv creates those elements with createElem . Like other tags IE also doesn't support html5 form elements like placeholde, aria-required, required etc etc . I want to know how can i get support for them ? Either html5shiv is enough for them or i have to look for another plugin?