How level of debt will afffect cost of capital

Hi, Sir.

I would like to ask, the higher the level of debt may result in the cost of equity rising, reducing the overall impact on the cost of capital.

Why higher debt would reduces the impact on cost of capital? Is it due to the debt being tax deductible?

Also, higher debt result in the cost of equity rising, is it due to the financial risk of using shareholder’s financing?